Energy
Conservation of Energy
Work
Power
Other Stuff
100
___________ is the energy of an object in motion.
What is kinetic energy?
100
When a ball is thrown directly upward, how does its energy change?
What is:
Kinetic energy is converted into potential energy
100
Work is a measure of...
change in energy
100
Which of the following is NOT a definition of power?
A. The rate of energy transfer
B. How many Joules are converted to other forms of energy
C. The rate at which work is done
D. How quickly energy is converted
B - this is the definition of WORK
100
Which force does the most work? Why?
C because it will go the farthest distance
200
Pulling back a rubber band is a form of storing ____________ energy.
What is potential energy?
200
If energy can be neither created nor destroyed, what do we mean when we say “Don’t waste energy!”
Use less energy to complete a task (be energy efficient)
OR: don't turn energy into less useful forms, like heat energy
200
What is the units for Work?
Joules
(or N*m)
200
Which uses more power, a student that runs up the stairs or a student that walks? Assume they have equal mass.
The running student - because the work is done in less time
200
Work has the same units as what other quantity?
Energy
300
Energy is a measure of an object’s __________.
What is "ability to do work"?
300
When a car rolls down a hill, most (but not all) of its potential energy converts to kinetic energy. Where does the rest go?
Heat/internal energy from friction
300
How much work is done if a 20 N force is used to slide a box 4 meters?
80 J
300
Calculate the power of a machine that can do 2400 J of work in 8 seconds. INCLUDE THE CORRECT UNITS!
300 W
300
An ice skater is gliding across the ice at a constant speed. Is she doing work? Why/why not?
No because no force means no work
400
What is the kinetic energy of a 15kg boulder resting at the top of a 12m cliff?
0 J
400
An object starting with 20 J of potential energy rolls down a hill. At the bottom, 90% of the potential energy has been converted to kinetic energy. How much energy (in Joules) was “lost” due to friction?
2 J
400
How much work is done if you push against a boulder with 200 N of force for 5 seconds but the boulder doesn’t move?
None!!!
400
How much energy does a 1500 W microwave use if it is on for 40 seconds?
60,000 J
400
A 10-newton force is required to hold a stretched spring 0.20 meter from its rest position. What is the spring constant? (Include units!)
50 N / m
500
What is the potential energy of a 15kg boulder resting at the top of a 12m cliff?
1764 J
500
A 2 kg object sits at the top of a 10 m hill. How fast will it be rolling at the bottom of the hill?
14 m/s
500
How much work is done to lift a 4kg barbell to a height of 2 m?
78.48 J
500
How powerful is a weight lifter who lifts a 400N weight 2 m in 1.6 seconds? (Solve for power)
500 W
500
A spring with a spring constant of 40 N/m is compressed .5 m. What is the potential energy stored in the spring? (Include units!)
5 J