Big Idea 13 Forces and Changes in Motion

Florida Next Generation Sunshine State Standards:

SC.5.P.13.1 – Identify familiar forces that cause objects to move, such as pushes or pulls, including gravity acting on falling objects.

SC.5.P.13.2 – Investigate and describe that the greater the force applied to it, the greater the change in motion of a given object.

Terms

English Spanish Haitian Creole1. attract atraer atire2. distance distancia distans3. force fuerza fòs

balanced forces fuerzas equilibradas fòs balance/fòs egalunbalanced forces fuerzas desequilibradas fòs inegal

4. friction fricción friksyon5. gravity gravedad gravite/pezantè6. magnetic magnético leman7. magnetism magnetismo mayetis8. motion movimiento deplasman9. position posición pozisyon

10. pull tirar/jalar rale11. push empujar pousad12. repel repeler/rechazar repouse13. speed velocidad vitès

Does This Matter to Me?

Would you like to drive a car someday? Maybe you already ride a bicycle or skateboard, or play baseball or soccer. All of these activities involve creating forces that make a car, bike, or ball move, go faster or slower, turn, or stop. Would you like to know how to make cars go faster or how to kick a soccer ball farther? Let’s learn about forces and motion so you can learn more about these activities. What do you already know about motion and force?

Talk within your group about these questions: How can we measure motion? How do forces affect the motion of objects?

Big Idea 13 63

Exploring the Motion of Objects(SC.5.P.13.1, SC.5.P.13.2)

Position refers to the location of an object. You can describe an object’s position by comparing it to the positions of other objects. Some words that describe an object’s position are right and left, above and below, or ahead and behind. Can you name other words that describe the position of an object?

Objects can move. How do you know that something has moved? You know that an object has moved because it is not in the same location or position as before. In science, motion occurs when an object’s position changes. An object that is in motion always changes its position and may change its direction and speed.

A force is a push or pull. Examples of forces include pushing to open a door, pushing a book across a desk, or pulling a wagon. Words that are used to describe forces include pushing, pulling, and twisting. Can you name other words used to describe forces?

Gravity is a force of attraction that exists between any two objects. The greater the mass of an object, the greater the gravitational force the object exerts.

Magnetism is another type of force. Think about what happens when two magnets are near each other. Magnets attract magnetic materials. Magnets also attract (pull together) and repel (push apart) other magnets.

Forces affect the way objects move or stop. Forces can also change the shape of an object through stretching or bending. The effect of force can be overcome by adding an equal or greater force in the opposite direction. For example, the force of Earth’s gravity must be overcome when a rocket launches into space. The rocket must exert an opposite force that is greater than the force of Earth’s gravity.

Big Idea 13 64

In Inquiry 4 below, you will explore the motion of objects and how motion can be measured.

Inquiry 4: How Does Height Affect the Time an Object Travels?(SC.5.P.13.1)

Inquiry Framework1. Questioning State the problem

When you release a marble from ramps of different heights, how does the length of time for the marble to cross the finish line change?

Make a predictionThe lower the height of the ramp, the more time it will take for the marble to cross the finish line.The higher the height of the ramp, the more time it will take for the marble to cross the finish line.Changing the height of the ramp will not affect the time it will take for the marble to cross the finish line.

2. Planning Read the materials and procedures Do I have all of the necessary materials?

Yes No

Have I read the procedures?Yes No

Summarize the procedures in your own words.

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

3. Implementing Gather the materials1 ramp (ruler with a groove)1 meter stick1 stopwatch1 marble3 identical size books (to set ramp height)masking tape

Follow the proceduresBig Idea 13 65

1. Make a ramp by placing one ruler end on the edge of one book.

2. Measure the height of the ramp in centimeters. Record the height in Data Table 1.

3. Using a meter stick, measure the distance that is one meter from the edge of the book. Place a piece of tape at this point. This is the finish line (see the graphic below).

4. Hold the marble at the 25-centimeter point on the ramp (see the graphic below).

5. When the timekeeper says, “Go,” release the marble to travel down the ramp.

6. Measure the time it takes for the marble to roll from the starting point to the finish line. Record the time in Data Table 1.

7. Repeat steps 4-6 for two additional trials.8. Add a second book to the ramp. Measure the height of the

ramp. Record the height in Data Table 1.9. Repeat steps 4-6 for a total of three trials.10. Add a third book to the ramp. Measure the height of the

ramp. Record the height in Data Table 1.11. Repeat steps 4-6 for a total of three trials.12. Calculate the average travel time for each set of three trials

for your group data in Data Table 1.13. Record the travel times for your class data in Data Table 2.14. Record the average travel time for your class data in Data

Table 3.The inquiry setup should look like the graphic:

Observe and record the results

Data Table 1: Travel Times for the Marble in Your Group

Ramp Height(cm)

Trial 1(seconds)

Trial 2(seconds)

Trial 3(seconds)

Average Travel Time (seconds)

1 Book _______ cm

2 Books _______ cm

3 Books _______ cm

Big Idea 13 66

Data Table 2: Travel Times for the Marbles in Your Class

1 Book 2 Books 3 Books

GroupRampHeight(cm)

AverageTravelTime

(seconds)

RampHeight(cm)

AverageTravelTime

(seconds)

RampHeight(cm)

AverageTravelTime

(seconds)

Group 1

Group 2

Group 3

Group 4

Group 5

Average

Data Table 3: Average Travel Times for the Marbles in Your Class

Average Ramp Height(cm)

Average Travel Time(seconds)

1. What were the variables in this investigation?

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

2. What was kept constant?

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Big Idea 13 67

3. Construct a graph for the travel times of your group data found in Data Table 1 and the average travel times of your class data found in Data Table 3. Do not forget to label your title.

The Effect of _____________________ on _______________________

Group Data from Data Table 1 Class Data from Data Table 3

4. Concluding Draw a conclusionWhat did you find out? Check the correct conclusion:

The lower the height of the ramp, the more time it took for the marble to cross the finish line.The higher the height of the ramp, the more time it took for the marble to cross the finish line.Changing the height of the ramp did not affect the time it took for the marble to cross the finish line.

Compare what you thought would happen with what actually happened. Did the results support your prediction?

Yes No

5. Reporting Share your resultsWhat do you want to tell others about the inquiry?Talk with your group members about what you did and what

Big Idea 13 68

Trav

el T

ime

(sec

onds

)

Ramp Height (centimeters)

you observed.

Produce a reportRecord what you did so others can learn. Write the answer to the following question:

When you released the marble from different heights on the ramp, how did the length of time for the marble to cross the finish line change?

__________________________________________________

__________________________________________________

__________________________________________________

__________________________________________________

__________________________________________________

6. Inquiry Extension Reflect on your results If I did this inquiry again, how would I improve it? What would be a good follow-up experiment based on

what I learned?

________________________________________________

________________________________________________

________________________________________________

________________________________________________

________________________________________________

7. Application Make connections How does this activity relate to what happens in the real

world? How could I apply the results in new situations?

________________________________________________

________________________________________________

________________________________________________

________________________________________________

Big Idea 13 69

________________________________________________

In this inquiry, you learned that when using the same release, the height of a ramp affected the time it took for a marble to travel. The greater the height of the ramp, the less time it took, or the faster the marble traveled to the finish line.

What did you measure in the inquiry? _______________________________________

______________________________________________________________________

What tool(s) did you use to measure? _______________________________________

What unit did you use to measure? _________________________________________

You measured how far the marble traveled, or the distance it traveled, along the meter stick. Distance is the length between two objects. To describe exactly how much an object has changed its position, we measure the distance that the object has moved from one location to another location. When an object moves from one location to another, distance and time are measured to see how fast or slow the object is moving. This is called speed. Speed is the distance an object travels in a certain amount of time. Speed is calculated by dividing the distance an object travels by the time it takes for the object to travel. The following formula describes speed:

Speed (s) = Distance (d) ÷ Time (t)s = d ÷ ts = d / t

Remember that distance is measured in units of length. Time is measured in units of time. Since speed is distance divided by time, the units for speed are represented as units of length per unit of time. For example, the metric units for speed are meters per second (m/s) or kilometers per hour (km/hr). Miles per hour is the customary unit used to measure speed.

Mass, Forces, and Motion(SC.5.P.13.2)

Balanced and Unbalanced Forces

Every object has mass. When all the forces on an object are balanced, the object’s motion will remain the same. If it is moving, it will continue moving. If it is still, it will stay still. In order to change the motion of an object, an unbalanced force is needed.

Big Idea 13 70

The boxing bag will not move untilan unbalanced force is applied to it.

Similar to the example in the picture above, a book resting on a desk has the force of gravity pulling it down and the force of the desk pushing it up. We know that the forces are balanced because the book is not moving. To get the book moving, another force must be added to push the book. This would be an unbalanced force.

You experience forces when you ride in a car. When the car begins to move, the force of the moving car changes the motion of your body until it is the same as the motion of the car. When the car suddenly stops, your body keeps moving forward until another force, like the force provided by a seatbelt, acts on you.

Your body keeps moving forward when the car suddenly stops. To stop your forward motion, the seatbelt provides resistance, or an unbalanced force.

Imagine trying to push a car that is in neutral. When the car is in neutral, it is not moving. To push a car and get it moving from the rest position, you would have to apply a lot of force. Now, think about pushing a toy car. That would be easy, and you would have to apply very little force to move it. What is the difference in the amount of force required to push the two objects? If you said that the toy car would be easier to push, you are correct. The mass of a real car is many times more than the mass of a toy car. As a result, getting a toy car to move and keep moving is much easier and takes much less force.

The rocks move in the direction of the applied force.It takes more force to move a large rock than a small rock.

Big Idea 13 71

When forces are equal in strength and in opposite directions, they cancel each other. These forces are called balanced forces. When the forces are not equal in strength and in opposite directions, they are called unbalanced forces.

When the forces are equal and opposite,they cancel each other.

The forces are called balanced forces.

Think about a game of tug-of-war with your friends. If both sides are pulling and neither side is moving, then the forces are balanced. How would you describe the forces if one person is taken away from the game?

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

When the forces are not equal and opposite,the forces are called unbalanced forces.

Friction

Friction is a force that resists motion. The motion of an object is slowed or stopped because of friction. A ball stops rolling, swings stop swinging, and a book that is pushed across a desk stops sliding because of the effects of friction from air or a surface. We cannot see friction but we can feel it. Rub your hands together. How did the force of friction feel to you? Friction occurs when two objects rub together. Different surfaces produce different amounts of friction. Some objects move across surfaces easily and other objects do not.

Big Idea 13 72

In the diagram, as a surface moves in the direction of the arrow, the rough surface has more “teeth” to get stuck on the wood surface than the smooth surface. This means that the friction between the rough surface and the wood is greater than the friction between the smooth surface and the wood. To reduce the amount of friction, the interaction between surfaces needs to be reduced. One way this is commonly done is by adding oil or water between surfaces. Adding oil or water puts more space between the surfaces, which reduces the resistance to movement between the surfaces, thus reducing the friction.

In Inquiry 5 below, you will investigate the force of friction.

Inquiry 5: How do Different Surfaces Affect Motion?(SC.5.P.13.1)

Inquiry Framework1. Questioning State the problem

How do different surfaces affect how far a marble travels?

Make a predictionThe marble will travel farthest on a smooth surface.The marble will travel farthest on a sandpaper surface.The marble will travel farthest on a cloth surface.

2. Planning Read the materials and procedures Do I have all of the necessary materials?

Yes No

Have I read the procedures?Yes No

Summarize the procedures in your own words.

________________________________________________

________________________________________________

________________________________________________

Big Idea 13 73

________________________________________________

________________________________________________

________________________________________________

________________________________________________

_______

3. Implementing Gather the materials1 ramp (ruler with a groove)1 meter stick1 marble1 textbook (to set ramp height)masking tapesmooth surface (for example, hard floor or long table)2 pieces of large grain sandpaper1 piece of cloth

Follow the procedures1. Make a ramp by placing a ruler on the edge of one book on

a smooth surface (for example, hard floor or long table).2. Hold the marble at the 25-centimeter point on the ramp,

aligning it with the book edge (see the graphic on the next page).

3. Release the marble to travel down the ramp.4. Place a small piece of masking tape at the place where the

marble stops. Measure the distance the marble rolled from the bottom end of the ruler/ramp to the tape ending point. Record the distance in Data Table 1.

5. Repeat steps 2-4 for two additional trials. Record the distance for each trial in Data Table 1.

6. Place sandpaper under the bottom end of the ruler/ramp, one in front of the other, extending outward toward where the marble will travel (see the graphic).

7. Repeat steps 2-4 for a total of three trials. Record the distance for each trial in Data Table 1.

8. Replace the sandpaper with the cloth, making sure to tuck one end of the cloth under the ruler (see the graphic).

9. Repeat steps 2-4 for a total of three trials. Record the distance for each trial in Data Table 1.

10. Calculate the average distance traveled for each surface type for your group data in Data Table 1.

11. Record the distances for your class data in Data Table 2.

Big Idea 13 74

The activity setup for the three surface types should look like the graphics below:

Observe and record the results

Data Table 1: Distance the Marble Traveled in Your Group

Surface(Type)

Trial 1(cm)

Trial 2(cm)

Trial 3(cm)

Average Distance (cm)

Smooth

Sandpaper

Cloth

Data Table 2: Average Distance the Marbles Traveled in Your Class

Smooth Sandpaper Cloth

GroupAverageDistance

(cm)

AverageDistance

(cm)

AverageDistance

(cm)

Group 1

Group 2

Group 3

Group 4

Group 5

Class Average

Big Idea 13 75

1. What were the variables in this investigation?

_________________________________________________

_________________________________________________

_________________________________________________

2. What was kept constant?

_________________________________________________

_________________________________________________

_________________________________________________

4. Concluding Draw a conclusionWhat did you find out?

The marble traveled farthest on _________________________.

Compare what you thought would happen with what actually happened. Did the results support your prediction?

Yes No

5. Reporting Share your resultsWhat do you want to tell others about the activity?Talk with your group members about what you did and what you observed.

Produce a reportRecord what you did so others can learn. Write the answers to the following questions:

1. How did different surfaces affect how far a marble traveled?

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

Big Idea 13 76

2. Which surface (smooth, sandpaper, or cloth) produced the most friction? Support your answer with evidence from your observations.

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

3. Which surface produced the least friction? Support your answer with evidence from your observations.

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

4. How does the distance the marble traveled relate to the amount of friction produced by each surface? Support your answer with evidence from your observations.

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

5. The mayor is planning to build a skateboarding park in your neighborhood. What type of surface (smooth or rough) should the builders use to maximize speed? Explain your reasoning.

_________________________________________________

_________________________________________________

Big Idea 13 77

_________________________________________________

_________________________________________________

_________________________________________________

6. Why is it important to drive slowly in the rain? Take a look at the picture below. Can you infer what is going to happen in each picture if the car makes a sudden stop?

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

6. Inquiry Extension Reflect on your results If I did this activity again, how would I improve it? What would be a good follow-up experiment based on

what I learned?

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

Big Idea 13 78

_________________________________________________

_________________________________________________

7. Application Make connections How does this activity relate to what happens in the real

world? How could I apply the results in new situations?

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

In this activity, you were able to observe how different surfaces resisted movement with different amounts of friction. You measured movement in centimeters to illustrate how the differences in surface types affected the force of friction. You should have concluded from this experiment that the rougher the surface, the greater the force of friction.

Magnetic Forces(SC.5.P.13.1)

Another type of force that we can measure is magnetic force. Magnets are all around us. Think about where you have seen magnets and then talk about them with a partner. Discuss how you know something is magnetic and other things are not magnetic. Work with your partner to make a list of four magnetic things that you have seen at school, at home, or in other places. Make sure to provide evidence that each item is magntic.

Magnetic Objects Provide evidence that it is magnetic1. Example: Alphabet letters on a

refrigeratorAre attracted to the refrigerator but not to wood

2.

3.

4.

Big Idea 13 79

Magnet Activity: What Happens When Magnets Come Together?

Let’s examine the forces of magnets. Your teacher will give your group two magnets called bar magnets. The ends of a magnet are called poles. One end is called the north pole (N) and the other end is called the south pole (S). Opposite magnetic poles (N-S) attract (pull together). Magnetic poles that are the same, called like magnetic poles, repel (push apart). For example, N-N are like magnetic poles, so they repel each other.

Explore some common objects around your desk to see if a magnetic force exists or not. Write the name of each object in the chart and tell whether there is a magnetic force.

Object Name Magnetic Force (Yes / No)

Pencil lead

Eraser

Paper Clip

Now work with your group to explore the poles of the bar magnets.Big Idea 13 80

1. Put the north poles (N) together and observe what happens.2. Put the south poles (S) together and observe what happens.3. Put a north pole (N) near a south pole (S) and observe what happens.

In the boxes below, draw 3 pictures to communicate what you observed with the magnets. Label your pictures with arrows and the words attract, repel, like, and opposite.

1. Two north poles

2. Two south poles

3. One north pole and one south pole

If a bar magnet is broken in half, each half will still have a north pole and a south pole. You cannot have a magnet with just one magnetic pole.

Big Idea 13 81

One common magnet is a doughnut magnet. You may be wondering where the poles are on a doughnut magnet. One face (top) of the doughnut magnet is the north pole (N) and the other face (bottom) of the doughnut magnet is the south pole (S).

Another common magnet is a horseshoe magnet. One end of a horseshoe magnet is the north pole (N) and the other end is the south pole (S).

You feel a magnetic force when magnets attract or repel. This is sometimes referred to as magnetic energy or magnetism.

Explain what would happen if the two magnets in the picture below were moved close together.

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

Big Idea 13 82

You learned about forces that act on objects and motion that occurs because of forces. You know that an object has moved because it is not in the same location or position as before. In science, motion occurs when an object’s position changes. You can measure the distance an object travels within a given time. This is called speed. Speed is calculated by dividing distance over time:

Speed = Distance ÷ Time.

To change the motion of an object, a force is needed. A force can change the speed of an object depending on its mass. The more mass an object has, the more force is required to change its speed.

Forces can work in pairs. When the forces are equal in strength and acting in opposite directions, they cancel each other. These forces are called balanced forces. When the forces are not equal in strength and acting in opposite directions, they are called unbalanced forces.

You investigated and found that friction is a force that opposes motion and resists pushes and pulls. We cannot see friction, but we can observe its effect when a rolling ball slows down until it stops or a playground swing stops swinging on its own (because of the friction of the air).

You also learned about other types of forces, including gravity and magnetism. Gravity is a force of attraction that exists between any two objects. A good example is the force of gravity between the Earth and you, which allows you to walk on the ground instead of floating away.

While examining magnets, you learned that magnets have two poles. You also observed a magnetic force between objects. When you placed like poles together, they repelled each other. When you placed opposite poles together, they attracted each other.

Big Idea 13 83

Assessment

1. Jose is a mechanic at an automobile repair shop. He spilled a can of oil on the concrete floor. The spilled oil will reduce which force?

a. Frictionb. Gravityc. Centripetald. Magnetism

2. A ball is sitting loose on a flat wagon that is going in the direction of the arrow. If the wagon suddenly stops, the ball will

a. Also suddenly stopb. Roll forward in the wagonc. Roll backward in the wagond. Bounce up and down

3. Susan designed an experiment to determine the speed of a toy car. She released the car from the top of a ramp. She already had a stopwatch. Which other tool should she use to measure the car’s speed?

a. Balanceb. Inclined planec. Spring scaled. Meter stick

Big Idea 13 84

4. The four balls below are about to be struck by a stick.

If the balls are hit with the same amount of force in the same direction, which ball will move the fastest and why?

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

5. An object moving along a surface suddenly increases speed. What can cause this to happen?

a. It is moved by balanced forces.b. It is moved by two opposite forces.c. It is moved by an unbalanced force.d. It moves on its own.

6. Two people are each pulling on the opposite ends of a rope. If they are pulling on the rope with equal but opposite forces, which of the following could happen to the rope?

a. It will stay in place between the two people.b. It will move toward the right.c. It will move toward the left.d. It will fall to the ground.

Big Idea 13 85

7. Which statement best describes what must happen in order for a person to lift an object?

a. The force of gravity must be greater than the mass of the object.b. The mass of the object must be greater than the force of gravity.c. The force of gravity must be greater than the upward pull or push on the object.d. The upward pull or push on the object must be greater than the force of gravity.

8. A student wants to arrange two bar magnets so that they repel each other. Which arrangement shows the best arrangement for the magnets to repel each other?

a.

b.

c.

d.

9. A student places one magnet above another magnet, as shown below.

Why does the top magnet appear to float above the bottom magnet?

a. The magnets are made of different material.b. The like poles (N and N, S and S) of the magnets repel each other.c. The opposite poles (N and S) of the magnets repel each other.d. The magnets have a different gravitational attraction.

Big Idea 13 86

10.The drawing below is of three separate bar magnets. The north and south poles of each magnet are labeled.

Which arrangement shows that the three magnets would attract one another, end to end?

a.

b.

c.

d.

Big Idea 13 87