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Chapter 10 Forces
Chapter Preview
10.1 The Nature of Force
10.2 Friction, Gravity, and Elastic Forces
10.3 Newton’s First and Second Laws
10.4 Newton’s Third Law
10.5 Rockets and Satellites
Table of Contents
Chapter 10 Forces
Chapter Preview Questions
1. How do you know an object is in motion?a. It has inertia.b. It has mass.c. It is changing position.d. It has a reference point.
Chapter 10 Forces
Chapter Preview Questions
1. How do you know an object is in motion?a. It has inertia.b. It has mass.c. It is changing position.d. It has a reference point.
Chapter 10 Forces
Chapter Preview Questions
2. What is velocity?a. speedb. speed in a given directionc. miles per hourd. change in speed over time
Chapter 10 Forces
Chapter Preview Questions
2. What is velocity?a. speedb. speed in a given directionc. miles per hourd. change in speed over time
Chapter 10 Forces
Chapter Preview Questions
3. Which is the best definition of acceleration?a. change in velocityb. change in reference pointc. increase in speedd. decrease in speed
Chapter 10 Forces
Chapter Preview Questions
3. Which is the best definition of acceleration?a. change in velocityb. change in reference pointc. increase in speedd. decrease in speed
Chapter 10 Forces
Chapter Preview Questions
4. If an object starts out at rest and accelerates to 100 m/s, what is its initial speed?
a. -100 m/sb. 0 m/sc. 100 m/sd. 32 m/s
Chapter 10 Forces
Chapter Preview Questions
4. If an object starts out at rest and accelerates to 100 m/s, what is its initial speed?
a. -100 m/sb. 0 m/sc. 100 m/sd. 32 m/s
Chapter 10 Forces
You drop a tennis ball anda baseball at the sametime. Why do the balls fallto the floor?
What causes an object’s velocity to change?
Chapter 10 Forces
Latin Word Origins
Latin Origin Meaning Key Term
centri- Center Centripetal force
Chapter 10 Forces
Latin Word Origins
Latin Origin Meaning Key Term
com- Together, with Compression
Chapter 10 Forces
Latin Word Origins
Latin Origin Meaning Key Term
jacere Throw Projectile
Chapter 10 Forces
Latin Word Origins
Latin Origin Meaning Key Term
premere Press Compression
Chapter 10 Forces
Latin Word Origins
Latin Origin Meaning Key Term
pro- Forward, before Projectile
Chapter 10 Forces
Latin Word Origins
Latin Origin Meaning Key Term
tensus Stretch Tension
Chapter 10 Forces
Apply It!
Look at pro- and jacere and predict the meaning of projectile.Revise your definition as needed as you read the chapter.Look for words with these Latin origins as you read the chapter.
Sample: I see that pro- means “forward” and that jacere means “to throw.”By combining the two I get the definition of projectile.
Chapter 10 Forces
End of Chapter Preview
Chapter 10 Forces
Section 1:The Nature of Force
How is a force described?How do balanced and unbalanced forces affect an object’s velocity?
Chapter 10 Forces
Combining Force VectorsThe strength and direction of the individual forces determine the net force.
Chapter 10 Forces
Unbalanced ForcesUnbalanced forces acting on an object result in a net force and cause a change in the object’s velocity.
Chapter 10 Forces
Balanced ForcesBalanced forces acting on an object do not change the object’s velocity.
Chapter 10 Forces
Links on Force
Click the SciLinks button for links on force.
Chapter 10 Forces
End of Section:The Nature of Force
Chapter 10 Forces
Section 2:Friction, Gravity, and
Elastic ForcesWhat factors determine the strength of the friction force between two surfaces?What factors affect the gravitational force between two objects?Why do objects accelerate during free fall?When is matter considered to be elastic?
Chapter 10 Forces
Gravity Between ObjectsThe force of gravity between objects increases with greater mass and decreases with greater distance.
Chapter 10 Forces
Mass and WeightThe gravitational force exerted on a person or object at the surface of a planet is known as weight.
Chapter 10 Forces
Free Fall
The graph shows how the speed of an object in free fall changes with time. Use the graph to answer the following questions.
Chapter 10 Forces
Free Fall
9.8 m/s; 29.4 m/s.
Interpreting Graphs:
What is the speed of the object at 1 second? At 3 seconds?
Chapter 10 Forces
Free Fall
The slope is 9.8. The speed increases by 9.8 m/s each second.
Calculating:
Calculate the slope of the graph. What does this number represent?
Chapter 10 Forces
Free Fall
58.8 m/s
Predicting:
Use the slope that you calculated in Step 2 to predict the object’s speed at 6 seconds.
Chapter 10 Forces
Free Fall
The object’s speed increases at a constant rate.
Drawing Conclusions:
The graph has a constant slope. What does the slope tell you about the object’s motion?
Chapter 10 Forces
Air ResistanceFalling objects with a greater surface area experience more air resistance.
Chapter 10 Forces
Links on Friction
Click the SciLinks button for links on friction.
Chapter 10 Forces
Free Fall
Click the Video button to watch a movie about free fall.
Chapter 10 Forces
End of Section:Friction, Gravity, and
Elastic Forces
Chapter 10 Forces
Section 3:Newton’s First and
Second LawsWhat is Newton’s first law of motion?What is Newton’s second law of motion?
Chapter 10 Forces
Calculating ForceA speedboat pulls a 55-kg water-skier. The skier to accelerates at 2.0 m/s2. Calculate the net force that causes this acceleration.
Read and Understand
What information have you been given?Mass of the water-skier (m) = 55 kgAcceleration of the water-skier (a) = 2.0 m/s2
Chapter 10 Forces
Calculating ForceA speedboat pulls a 55-kg water-skier. The skier accelerates at 2.0 m/s2. Calculate the net force that causes this acceleration.Plan and SolveWhat quantity are you trying to calculate?
The net force (Fnet) = __What formula contains the given quantities and the unknown quantity?
a = Fnet/m or Fnet = m x aPerform the calculation.
Fnet = m x a = 55 kg x 2.0 m/s2
F = 110 kg • m/s2
F = 110 N
Chapter 10 Forces
Calculating ForceA speedboat pulls a 55-kg water-skier. The skier accelerates at 2.0 m/s2. Calculate the net force that causes this acceleration.
Look Back and Check
Does your answer make sense?A net force of 110 N is required. This does not include the force that overcomes friction.
Chapter 10 Forces
Calculating ForcePractice Problem
What is the net force on a 1,000-kg object accelerating at 3 m/s2?
3,000 N (1,000 kg x 3 m/s2)
Chapter 10 Forces
Calculating ForcePractice Problem
What net force is needed to accelerate a 25-kg cart at 14 m/s2?
350 N (25 kg x 14 m/s2)
Chapter 10 Forces
More on Newton’s Laws
Click the PHSchool.com button for an activity about Newton’s laws.
Chapter 10 Forces
End of Section:Newton’s First and
Second Laws
Chapter 10 Forces
Section 4:Newton’s Third Law
What is Newton’s third law of motion?How can you calculate the momentum of an object?What is the law of conservation of momentum?
Chapter 10 Forces
Newton’s Third Law of MotionNewton’s third law of motion states that if one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.
Chapter 10 Forces
Calculating MomentumWhich has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s, or a 4.0-kg sledgehammer swung at 0.9 m/s?
Read and Understand
What information are you given?Mass of smaller sledgehammer = 3.0 kgVelocity of smaller sledgehammer = 1.5 m/sMass of larger sledgehammer = 4.0 kgVelocity of larger sledgehammer = 0.9 m/s
Chapter 10 Forces
Calculating MomentumWhich has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?Plan and SolveWhat quantities are you trying to calculate?
The momentum of each sledgehammer = __What formula contains the given quantities and the unknown quantity?
Momentum = Mass x VelocityPerform the calculation.
Smaller sledgehammer = 3.0 km x 1.5 m/s = 4.5 kg•m/sLarger sledgehammer = 4.0 km x 0.9 m/s = 3.6 kg•m/s
Chapter 10 Forces
Calculating MomentumWhich has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?
Look Back and Check
Does your answer make sense?It is possible for the 3.0-kg hammer to have more momentum than the 4.0-kg one because it has a greater velocity.
Chapter 10 Forces
Calculating MomentumPractice Problem
A golf ball travels at 16 m/s, while a baseball moves at 7 m/s. The mass of the golf ball is 0.045 kg and the mass of the baseball is 0.14 kg. Which has greater momentum?
Golf ball: 0.045 kg x 16 m/s = 0.72 kg•m/sBaseball: 0.14 kg x 7 m/s = 0.98 kg•m/sThe baseball has greater momentum.
Chapter 10 Forces
Calculating MomentumPractice Problem
What is the momentum of a bird with a mass of 0.018 kg flying at 15 m/s?
0.27 kg•m/s (0.018 kg x 15 m/s = 0.27 kg•m/s)
Chapter 10 Forces-
Conservation of MomentumIn the absence of friction, momentum is conserved when two train cars collide.
Chapter 10 Forces
Momentum Activity
Click the Active Art button to open a browser window and access Active Art about momentum.
Chapter 10 Forces
End of Section:Newton’s Third Law
Chapter 10 Forces
Section 5:Rockets and Satellites
How does a rocket lift off the ground?What keeps a satellite in orbit?
Chapter 10 Forces
What Is a Satellite?A projectile follows a curved path. The horizontal and vertical motions act independently.
Chapter 10 Forces
What Is a Satellite?The faster a projectile is thrown, the father it travels before it hits the ground. A projectile with enough velocity moves in a circular orbit.
Chapter 10 Forces
What Is a Satellite?Depending on their uses, artificial satellites orbit at different heights.
Chapter 10 Forces
End of Section:Rockets and Satellites
Chapter 10 Forces
QuickTake Quiz
Click to start quiz.
