Ms. Moore 10/1/12. Energy is required for any change that occurs, no matter how small. Energy is...
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Transcript of Ms. Moore 10/1/12. Energy is required for any change that occurs, no matter how small. Energy is...
Energy
Ms. Moore10/1/12
What is energy?
Energy is required for any change that occurs, no matter how small. Energy is the ability to cause change. Examples:
Forms of energy: Electrical Chemical Radiant Thermal
Energy can be stored and move from place to place.
Kinetic Energy
Kinetic energy (KE) is the energy a moving object has because of its motion. The kinetic energy of a moving object
depends on an object’s mass and its speed.
Kinetic energy (joules) = ½ mass (kg) x speed2 (m/s)
Practice Problems
A baseball with a mass of 0.15kg is moving at a speed of 40m/s. What is the baseball’s kinetic energy?
A sprinter has a mass of 80kg and a kinetic energy of 4,000 J. What is the sprinter’s speed?
A car with a mass of 1,500kg doubles its speed from 50km/h to 100km/h. By how many times does the kinetic energy of the car increase?
Lab
Read the mini lab found on page 103.
Create a table of your results and be ready for a discussion.
How did the take off speed of the nickel depend on the distance that you stretched the rubber band?
How did the KE of the nickel depend on the distance the rubber band was stretched?
Potential Energy
Energy doesn’t have to involve motion. Motionless objects have energy.
Potential energy (PE) is stored energy due to position. Examples:
3 Types of PE:
Elastic potential energy is energy stored by something that can stretch or compress Rubber band or spring
Chemical Potential Energy is energy stored in chemical bonds Food and gasoline
Gravitational Potential Energy (GPE) is energy stored by objects due to the position above Earth’s surface. Depends on the objects mass and height
above the ground.
GPE (j) = mass (kg) X 9.8 (m/s2) X height (m)
Practice Problems
Find the GPE of a coffee mug with a mass of 0.3kg that is on a counter top 1m high above the ground.
How high above the ground is a baseball with a mass of 0.15kg that has a GPE of 73.5J?
A rock climber is 200m above the ground and has a GPE of 117,600J. What is the rock climber’s mass?
Lab: Bouncing Balls
Why do bouncing balls stop bouncing?
Refer to page 106
Measure tennis ball vs. bouncy ball
Include a table of results