STAAR Review

A quick Glance.

Are you ready for the big GAME

Overview

• Forces and Motion– Formula Chart Review– Energy Transformations– Potential and Kinetic Energy– Balanced and Unbalanced Forces – Graphing Motion– Work and Simple Machines– Waves

• Energy has no mass or weight

• Energy does not take up space

• Energy is NOT

matter

Energy vs. MatterEverything on Earth is either energy or matter

• Matter has mass and weight• Matter takes up space• Matter is NOT energy

Energy is the ability to do work

FORMS OF ENERGY• Thermal- the total potential and kinetic energy based on the

vibrations and movements of atoms and molecules. Examples- friction, changes in state of matter

• Chemical Energy- is stored in chemical bonds. Energy is released when chemicals are broken apart. New molecules are then formed. Example- digestion, burning match, photosynthesis

FORMS OF ENERGY• Mechanical Energy- energy of motion-

moves objects. Examples- water in a waterfall, wind, moving vehicles

• Radiant- Energy carried by light. All life on earth is dependent on radiant energy from the sun. Examples- radio waves (AM, FM, TV), microwaves, X-rays, and plant growth.

• Electrical- energy of electrons moving along a path (electrical current). Examples- power lines carry electricity, electric motors are driven by electromagnetic energy

• Nuclear Energy stored in the nucleus of an atom. Energy is released through the splitting of an atom. Examples- fission, or fusion in the production of sunlight

Energy TransformationsEnergy Transformations

• The most common energy conversion involves the changing of potential energy into kinetic energy or vice-versa.

Examples:• Ball thrown in the air• Roller coaster

• During energy transformations, energy is often released as light, heat, or sound.

• Law of Conservation of Energy – Energy can be changed into many forms; it is never lost.

Energy conversions

Clock Electrical Light/soundBattery Chemical ElectricalLight bulb Electrical Light/thermalBlender Electrical MechanicalSolar Panel Sunlight ElectricalPhotosynthesis Sunlight ChemicalCD Player Electrical MechanicalDam Mechanical ElectricalWindmill Mechanical Electrical

Energy Transformations Checkpoint 4.1

Diesel fuel is used in the engines of the machines and trucks at a quarry. Which of these is the main energy transformation as the fuel is used by the engines?

F Electrical energy is converted to heat energy.G Heat energy is converted to potential energy.H Electrical energy is converted to kinetic

energy.J Chemical energy is converted to kinetic

energy.

Potential and Kinetic Energy

• Potential- stored energy, due to an objects position

• Kinetic- energy of motion based on the mass and speed of the moving object

POTENTIAL ENERGY

• Potential Energy (PE) is energy an object has because of its position.

• Potential energy (PE)=the mass of an object (x) gravity (x) it’s height.

• PE is stored energy.

KINETIC ENERGY• Kinetic energy (KE) is

the energy of motion.

• Only a moving object has kinetic energy

• Amount of energy depends on speed and mass.

Kinetic Energy

• Mass- An object with more mass has more kinetic energy than an object with less mass if both are traveling at the same speed.

• Speed- The faster an object moves the greater its kinetic energy.

Roller Coaster• The cars of a roller coaster

have the greatest potential energy at the top of the first hill. As they start their descent, the cars lose potential energy and they gain kinetic energy - the energy of motion. Throughout the ride, each time the train loses height, it gains speed as potential energy is transformed into kinetic energy. Likewise, each time it gains height, it loses speed as kinetic energy is transformed into potential energy.

Energy Transformations

Wind has kinetic energy which can be transformed into other forms of energy.

Hydropower depends on the transformation of potential energy to kinetic energy. The kinetic energy of the fast-moving water turns turbines, which drive generators that produce electricity.

The energy in fossil fuels (coal, oil, gas) is chemical potential energy. Fossil fuels come from decayed living matter that has stored energy in its chemical bonds.

Potential and Kinetic Energy Checkpoint 4.2

The diagram above shows a barrel moving toward a waterfall. The barrel will have the greatest potential energy at which of these locations?

A WB XC YD Z

Motion

• Frame of Reference -Object or point from which motion is determined

• Motion is a change

in position relative to

a frame of reference

What is motion?

• If you are standing in one place, and your friend walks by you, are you moving relative to your friend?– Is your friend moving relative to you?– Is either of you moving relative to the earth?

Speed

• Speed = Distance ÷ Time

S= D

T

Example: A car travels 300km in 6 hours. What is the speed of the car?

Answer:

• Speed = distance ÷ time

• Speed = 300km ÷ 6 hours

• Speed = 50km/hr

Distance-time graphs

• On your paper, graph the following:– D (m) T (sec)

0 0 5 7 10 14 15 21

Distance-time graphs

Is your graph a straight line?

• A distance-time graph which is a straight line indicates constant speed.

• In constant speed, the object does not speed up or slow down. The acceleration is zero.

Graph the following on a distance-time graph:

• D (m) T (s) 0 0 5 1 20 245 380 4125 5

Does your graph curve?

0 1 2 3 4 5

• A graph that curves on a distance-time graph shows that the object is accelerating.

Distance-time graphs

• Describe the motion of the object as shown in the graph.

•From 0-8 sec, constant speed: (25 m/sec);•From 8-12 sec, no motion; •From 12-16 sec, acceleration;•From 16-20 sec, constant speed

Speed-time graphs

• Using the distance-time graph from the last frame, draw a speed time graph.

Average Speed (m/s) Time (sec)

25 0 to 8

0 8 to 12

37.5 12 to 20

What does your graph look like?

• Constant speed will be a horizontal line on a speed time graph.

• If the speed decreases, the line will slant down.

• If the speed increases, the line will slant up.

What do the following speed-time graphs depict?

Graphing Motion Checkpoint 4.3•

1 The graph shows the movement of a car over time. What is the car’s average speed?

F 10 kilometers per hourG 15 kilometers per hourH 30 kilometers per hourJ 60 kilometers per hour

Force

• A force is a push or a pull.

• A force always acts in a certain direction. – When you push on a

door, the force is in the direction of the push.

– When you pull on a doorknob, the force is in the direction of the pull.

Forces in Living Systems• The body uses force;

– To move body parts, when you bend your arm your one muscle contracts to exert force while the other muscle relaxes.

– During breathing muscles contract to move air in and out of the lungs.

– The heart also contracts to pump blood through the blood vessels, carrying oxygen

• Fish exert force to swim by pushing against the water.

• Plant Seedlings exert force on the surrounding soil to emerge from the ground.

Balanced Forces

• To describe a force, you must know two things-the size of the force and the direction of the force. – For example, think about two teams in a tug

of war. – Each team pulls with equal force in opposite

directions.– Neither team can make the other move.

Balanced Forces (2)

• Forces that are equal in size and opposite in direction are called balanced forces.

Unbalanced Forces

• Unbalanced forces cause a change in the motion of an object.

• The forces acting on the rope are no longer balanced.

Forces and Motion • Unbalanced forces can change the motion of an

object in two ways. – When unbalanced forces act on an object at rest, the

object will move.– When unbalanced forces act on a moving object, the

motion of the object will change. The object may speed up, slow down, stop moving, or change direction.

Solving for Force

• An unbalanced force acting on an object equals the object’s mass times its acceleration.

F = m x a

Force is measured in Newtons.

Acceleration: a measurement of how quickly an object is changing speed.

Friction

• Flying baseballs slow down and eventually stop because of the force of gravity.

• Cars and bikes eventually slow down and stop because of the force of friction.

• Types of friction:

• a. Static (usually the greatest)

• b. Sliding

• c. Rolling (usually the least)

Balanced and Unbalanced Forces Checkpoint 4.4

If a force is applied for 15

seconds, in which situation

will the box be moved the

greatest distance?

WORK

• Work is done when a force causes an object to move in the direction that the force is applied.

• The formula for work is: W = F X D

• If there is no movement, there is no work.

Formula Chart

The Unit of Work is the Joule

Force x Distance = Work–1 Newton x 1 meter = 1 Newton meter

–1 Newton meter = 1 Joule

Example 1:

• A high jumper weighs 700 newtons. What work does the jumper perform in jumping over a bar 2.0 meters high?

• Answer: W = F x d

• W = 700N x 2.0 m

• = 1400 nm

• = 1400 Joules

Use your Formula Chart

Work and Simple Machines

Two things must happen for work to be done.

• A force must be applied to an object

• The object must move in the same direction as the force.

Simple machines are used to make work easier.

What is a Simple Machine?

• Simple machines make work easier– Reduce input force but

work remains the same.– Change the size and

direction of force. – Do work with one

movement

• A simple machine has few or no moving parts.

Wheels and Axles

• The wheel and axle are a simple machine

• The axle is a rod that goes through the wheel which allows the wheel to turn

• Gears are a form of wheels and axles

Pulleys

• Pulleys are wheels and axles with a groove around the outside

• A pulley needs a rope, chain or belt around the groove to make it do work

Inclined Planes

• An inclined plane is a flat surface that is higher on one end

• Inclined planes make the work of moving things easier

Wedges

• Two inclined planes joined back to back.

• Wedges are used to split things.

Screws

• A screw is an inclined plane wrapped around a shaft or cylinder.

• The inclined plane allows the screw to move itself when rotated.

Levers-First Class

• In a first class lever the fulcrum is in the middle and the load and effort is on either side

• Think of a see-saw

Note: The fulcrum is a pivot point that changes the direction of the force.

Moving the fulcrum changes the distance each arm moves under a force.

Levers-Second Class

• In a second class lever the fulcrum is at the end, with the load in the middle

• Think of a wheelbarrow

Levers-Third Class

• In a third class lever the fulcrum is again at the end, but the effort is in the middle

• Think of a pair of tweezers or fishing pole

Simple Machines Checkpoint 4.5

The girl in the picture above is using a lever to lift a heavy box. Using the lever makes the girl’s task easier by —

A reducing the input forceB reducing the box’s massC increasing the amount of work doneD increasing the distance the box is lifted

Waves

• By moving a rope regularly up and down, a traveling or periodic wave is produced. Waves transfer energy from one place to by vibrating something up and down, or back and forth.

A transverse wave is a wave in which the particles of the medium are displaced in a direction perpendicular to the direction of energy transport.

Wave Characteristics

. The crest of a wave is the point on the medium which exhibits the maximum amount of positive or upwards displacement from the rest position.

Wave Characteristics

The trough of a wave is the point on the medium which exhibits the maximum amount of negative or downwards displacement from the rest position

The amplitude of a wave refers to the maximum amount of displacement of a particle on the medium from its rest position. The amount of energy carried by a wave is related to the amplitude of the wave.

A longitudinal wave is a wave in which the particles of the medium are displaced in a direction parallel to the direction of energy transport.

• A compression is a point on a medium through which a longitudinal wave is traveling which has the maximum density. A region where the coils are spread apart, thus maximizing the distance between coils, is known as a rarefaction. A rarefaction is a point on a medium through which a longitudinal wave is traveling which has the minimum density.

A tuning fork serves as a useful illustration of how a vibrating object can produce sound.

Characteristics of Waves: Frequency – the number of complete waves passing a point in space per second; depends on the source Wavelength – the distance from a point in a wave to the next point that wave in the same phase.

• Light waves will always travel in a straight line until they hit a barrier. So whether its traveling through air, water, glass, diamond, or any substance (or none at all), light travels in a straight path, until it encounters a different medium.

All visible objects either emit light or reflect light. When an object either emits light or reflects it, the

light travels in all directions from the object. If viewed through a pinhole the light rays encounter no different medium so they travel in a straight line.

Waves

• Sound is the movement of energy through substances in longitudinal (compression/rarefaction) waves. Sound is produced when a force causes an object or substance to vibrate––the energy is transferred through the substance in a wave.

Waves Checkpoint 4.6

In the diagram above, at which point are the sound waves being generated?

A RB SC TD V