Definitions
The ability to do work
Energy
If you push on a wall and it doesn't move, how much work is done?
A parked car at the top of a hill has mostly this type of energy:
A flashlight converts this type of energy into light energy.
chemical energy
Which requires more work: lifting a book 1 meter or 2 meters
2 meters
This occurs when a force causes an object to move
Work
A force of 10 N pushes an object 5m. How much work is done?
W= F x D
Work = 50J
If speed doubles, what happens to kinetic energy?
It quadruples (increase 4x)
A roller coaster going down a hill transforms energy from ___ to ___.
potential → kinetic
Why is it harder to stop a fast-moving object than a slow one
it has more kinetic energy
How fast work is done
Power
If two students lift the same box, but one does it faster. Who has more power?
The faster student.
A 6 kg object moves with a velocity of 4m/s. What is the kinetic energy?
KE= 1/2 mv2
48 J
In a toaster: electrical → ______ energy.
thermal (heat) energy
Why do roller coasters start high?
to have more potential energy
Energy due to motion
Kinetic Energy
If you double the force but keep distance the same, what happens to work?
Work Doubles
A 5kg object is lifted 2 m. What is the gravitational potential energy?
PE=mgh
100 J
A stretched rubber band stores this type of energy.
elastic potential energy
Why does a heavier object require more work to lift?
greater force (weight)
Stored energy based on a position or shape.
Potential Energy
You do 200J of work in 10 seconds. What happens to power if time is cut in half?
Power Doubles
If a spring has a constant of 32 n/m and pushes a cart a distance of 1 m. What is the Kinetic energy released by the spring?
EPE = 1/2 kx2
16 J
A phone playing music: electrical → ______ → sound
mechanical energy
Two students carry identical backpacks up the same flight of stairs.
Both reach the top.
Question:
Who does more work, who has more power, and why?
Work: They do the same amount of work
Power: Student B (the faster one) has more power