Download Calculating Work and Energy Word Problems

Calculating Work and Energy
Name:______________________
Class#:_____________________
Remember the steps we use for solving equations:
1. Underling the variables and circle the values. (If the variable is not listed,
write it above the value.)
2. Box the variable you are trying to find.
3. List the variables and values in a column.
4. Find and write the equation that has the variable you are looking for
alone on one side of the equal sign.
5. Plug in the values you know for the variables in the equation.
6. Solve the equation.
7. Circle your answer and check your units.
Here are the equations you might need:
F=ma
p=mv
W=Fd
agravity=g=10m/s2
PE=mgh
KE=½mv2
1. A student’s full backpack with a weight of 30N. She lifts it from the floor to a
shelf with a height of 1.5m. How much work is done on the pack full of books?
2. A dancer lifts a 400 N ballerina overhead a distance of 1.4 m and holds her
there for several seconds. How much work is done during the lift?
3. While performing a chin-up, Carlos raises himself 0.5 m. How much does
Carlos weigh in Newtons if he does 300J of work in his chin-up?
4. Sam is putting in a new countertop in his kitchen and lifts a 80kg granite slab
from the floor to the counter, a distance of 0.8 m. How much work did he do on
the slab of rock? (Hint: This is a two step problem, find force first, then work.)
5. A 30 kg child climbs 15 meters up a tree. When he stops to have a look
around, what is the child’s potential energy?
6. A cat climbs upwards 12 meters to sit on the roof of a house. While sitting on
the roof, the cat has 240 J of potential energy. What is the mass of the cat?
7. What is the kinetic energy of a 45 kg object moving at 13m/sec?
8. A carpenter lifts a 45 kg beam 1.2 m. How much work is done on the beam?
(Remember that you have to find the weight of the 45kg beam using the fact
that acceleration from gravity is 10m/s2.)
9. A boulder has 5000 J of potential energy while sitting on top of a cliff. If the
cliff is 250 meters above the ground, what is the mass of the boulder?
10. A 6 kg thrown with a catapult with a velocity of 10m/s. What is the kinetic
energy of the rock?
Extra Credit: (Do on back)
A student with 3600 J of potential energy stands on a diving board 7.2m up.
What is the velocity of the person the instant before she hits the water?