Download 2017WorkEnergyandPowerworksheet

PCB 2H Practice Problems
Name________________
Work, Energy, and Power:
1. A force of 800 Newtons is needed to push a car across a lot. Two students push the car 40
meters. How much work is done?
32000 J or 32 kJ
2. How much work is done in lifting a 60 kg crate a vertical distance of 10 meters? What if the crate
is carried 10 meters in a horizontal direction?
5880 J
3. Explain the statement, "Atlas did no work".
4. Calculate the kinetic energy of a 2.0 g grape moving at 500 m/s.
No distance = no work
250 J
5. A. What is the gravitational potential energy of a 1.2 kg watermelon if it is 2.4 m above the ground?
28.2 J
B. What is the kinetic energy half way down? 14.1 J
6. What is the velocity of a jogger with a mass of 65 kg and kinetic energy of 203 joules? 2.5 m/s
7. A. An apple tree has a gravitational potential energy of 175 J and a mass of 0.36 kg.How high from the
ground is the apple? 49 m
B. What is the speed of the apple when just before it hits the ground? 7.04 m/s
8. A 500 kg roller coaster starts from rest 60 m above the ground. How fast will it be going when it gets
to the ground? 34.6 m/s
9. A box car at the top of a 500 m hill has a gravitational potential energy of 11050 Joules.
a. What is the mass of the car? 2.26 kg
b. Assuming energy is conserved and there is no friction, how much speed does the car have at
20m from the bottom of the hill? 98.9 m/s
10. Your family is moving to a new apartment. While lifting a box 1.5m straight up to put it on a truck
you exert an upward force of 200N for 1.0 s. How much power is required to do this? 300 Watts
11. You lift a book from the floor to a bookshelf 1.0m above the ground. How much power is used if the
upward force is 15 N and you do the work in 2 s? 7.5 Watts
12. You apply a horizontal force of 10 N to pull a wheeled suitcase at a constant speed of .5 m/s across a
flat ground. How much power is used? 5 Watts
Equations
Fg = m g
UNITS: (kilograms) (9.8 m/s2) = Newtons
Work = F d
UNITS: (Newtons) (meters)= joules
Power = work / time
Units: joules / seconds = Watts
Gravitational Potential Energy = mgh
Kinetic Energy = ½ mv2