Name ___________________ Date _________ Block ____
Work, Energy, Power and Momentum!!!
1) A man pushes against a car stuck in a snow bank with a force of 220N, while his date sits nervously
behind the steering wheel trying not to make the tires spin. They try this for 10nim. However, the car
does not move. How much work did he do on the car?
2) If frictional forces and air resistance were acting upon a falling ball would the kinetic energy of the ball
just prior to striking the ground be more, less, or equal to the value if frictional forces and air resistance
weren’t there?
Use the following picture to answer the next three questions.
3) As the object moves from point A to point D across the surface, the sum of its gravitational potential and
kinetic energies does what? (increase?... ect)
4) The object will have a minimum gravitational potential energy at what point?
5) The object's kinetic energy at point C is less than its kinetic energy at what point?
6) Two baseballs are fired into a pile of hay. If one has twice the speed of the other, how much farther does
the faster baseball penetrate?
7) Use the law of conservation of energy (assume no friction) to fill in the blanks at the various marked
positions for a 1000-kg roller coaster car.
8) If the angle of the initial drop in the roller coaster diagram above were 60 degrees (and all other factors
were kept constant), would the speed at the bottom of the hill be any different? Explain.
9) Determine Mr. Williams’ (a mass of approximately 50 kg) speed at locations B, C, D and E. How does it
change as Mr. Williams rides the slopes?
10) Sally carries a 25kg text book under her arm along a horizontal path, through the school. She uses a
force of 57N to hold the book. It takes her 2min to get to class. How much work was done on the text
book?
11) Tommy does 15 Joules of work to push the pencil over 1 meter. How much force did he use?
12) A toy car on frictionless coasters is pushed 5 m along a ramp that makes an angle of 20º to the ground.
1960N of force is required to do this. How much work was done on the cart?
13) A 100 kg object is pulled vertically upward 5.0 m by a rope with an acceleration of 1.0 m/s2. Find the
work done by the tension force in the rope.
14) The baseball player does 1234 Joules of work when hitting a baseball into left field. Assuming the
baseball landed 100 meters away from home plate, how much force did the player use to hit the ball?
15) What is the kinetic energy of a 750g baseball that is moving at 175 km/hr?
16) A toy cart moves with a kinetic energy of 30 J. If its speed is doubled, what is its kinetic energy?
17) What is the potential energy of a full, stuck rollercoaster car is it stopped on the top of a hill that was 75
feet high and has a mass of 500kg. The coaster holds 25 people with an average mass of 200kg. (39 in =
1 m)
18) If a swing has 400J of potential energy at the top of its path, and only 96J of PE at the bottom of its path,
how much kinetic energy does it have at the bottom of its path, if energy is perfectly conserved?
19) If the swinger in the previous question has a mass of 75kg what is the initial and final height of the
swing?
20) If I dropped a marker with a mass of .25kg from a height of 2.5m (and all energy is conserved), how
much sound + heat energy will be released when all of its kinetic energy is converted as it hits the
ground.
21) A box that weighs 1000N is lifted a distance of 20m in 10s. How many kilowatts of power are
produced?
__________ a 100 watt lightbulb burns for 2 hours
22) Rank the following items from
__________ a 40 watt lightbulb burns for 4 hours
lowest power requirement to
highest power requirement.
__________ a 1500 watt hair dryer is used for 0.5 hours
23) At a tractor pull, one machine
__________ a 500 watt microwave operates for 0.5 hours
has a run that produces 28,000
__________ a 15 watt compact fluorescent light burns for 10 hours
Joules in 2 seconds. How many
Watts of power did this tractor
produce?
24) What was the horsepower produced by the tractor in the previous question?
25) If 4 kW of power is dissipated for 30 min, how much energy was used?
26) Calculate how much it would cost to operate a 1000 watt spotlight for one 8 hours if 1 kilowatt hour
costs $0.15.
27) An 8,500-kg car increases its velocity from 35 m/s to 55 m/s in 6 seconds.
(A) What is its change in kinetic energy?
(B) What power had to be developed?
28) The hopper of a concrete hoist is capable of holding 750 lb when it is half full. If this hopper is
moved to an elevation of 165 ft in 6sec.
(A) What is the increase in potential energy?
(B) What power, in H.P., must be developed?
(C) What power, in watts, must be developed?
29) Distinguish between mass and momentum. Which is inertia and which is inertia in motion?
30) In terms of momentum conservation, why does a cannon recoil when fired?
31) What does it mean to say that momentum is conserved?
32) Imagine that you are hovering next to the space shuttle in an Earth orbit. Your buddy of equal mass,
who is moving at 4 km/h with respect to the shuttle, bumps into you. If he holds onto you, how fast do
you both move with respect to the ship?
33) (a) What is the momentum of an 8-kg bowling ball rolling at 2 m/s?
34) (a) What is the momentum of a 50-kg carton that slides with 4 m/s across an icy surface? (b) The sliding
carton skids onto a rough surface and stops in 3s. Calculate the force of friction it encounters.
35) A 2-kg blob of putty moving at 3 m/s slams into a 2-kg blob of putty at rest. (a) Calculate the speed of
the two stuck-together blobs of putty immediately after colliding. (b) Calculate the speed of the two
blobs if the one at rest was 4-kg.
36) Work is measured in the same units as:
37) A ball is thrown vertically upward into the air. As it rises, there is an increase in what?
38) As the velocity of a body is halved, its kinetic energy is ________.
39) Work is done when what happens?
40) In order to compute power, one must know what?
41) In a waterfall, energy is converted from what to what?
42) The kinetic energy of an object depends upon its….?