Work, Energy, Power, and Force
How are energy and motion related?
It takes energy for motion to occur
A force of 10 N is used to move an object 5 m. How much work is done?
(work=Force X Distance)
W = 10 N × 5 m = 50 J
Kinetic energy is the energy of......
Motion, moving
Explain why a book sitting on a shelf has gravitational potential energy.
The book has gravitational potential energy because it is elevated above the ground and could fall due to gravity.
Is work done when you hold a heavy object? Why or why not?
It takes force to hold an object, but no work is done if the object does not move a distance.
A student does 120 J of work in 6 seconds. What is the power output? (Work = Force X distance=power so Power = Work/time)
P = 120 J ÷ 6 s = 20 W
Potential Energy is the energy of.....
Possibility, it has the possibility to do work
How does increasing an object’s speed affect its kinetic energy?
Increasing speed increases kinetic energy.
How are power and work related to each other?
Power is the rate at which work is done. It shows how fast energy is transferred.
Two students lift the same box. One takes 4 seconds, the other takes 8 seconds. Who uses more power and why?
The student who lifts the box in 4 seconds uses more power because the same work is done in less time
Explain why a running deer has kinetic energy.
The deer is moving and kinetic energy is energy of motion.
A soccer ball is kicked and rolls across the field. When does it have kinetic energy?
The soccer ball has kinetic energy while it is moving.
Which requires more power: lifting the same object quickly or lifting it slowly? Why?
Lifting the object quickly requires more power because the same work is done in less time.
An object is moved 8 m with 40 J of work. What force was applied? (Force = Work ÷ Distance)
F = 40 J ÷ 8 m = 5 N
Several people are using bows to shoot arrows at targets. At what point do the bows have elastic potential energy? At what point do they have kinetic energy?
The bows have elastic potential energy when the arrows are drawn back as far as they will go on the bow strings. The arrows have kinetic energy when they are released and are moving forward.
Why does a stretched rubber band have elastic potential energy?
It has elastic potential energy because it is stretched and can return to its original shape.
How does distance affect the amount of work done on an object?
The farther an object moves, the more work is done when the same force is applied.
A force of 35 N is used to move an object 8 m. How much work is done? (Work = Force × Distance)
What is the main difference between gravitational potential energy and elastic potential energy?
Gravitational depends on height and elastic depends on shape.
Explain why a running deer has kinetic energy.
The deer is moving and kinetic energy is energy of motion.