*REGENTS PHYSICS WORK AND
ENERGY*

*MR. GAGNON
REVIEW*

* *

1.) Two people of the same
mass climb the same flight of stairs. The first person climbs the stairs in 25
seconds. The second person takes 35 seconds. Which person does the most work?
Which person expends the most power? Explain your answers.

2.) A box that weighs 1000
Newtons is lifted a distance of 20.0 meters straight up by a rope and pulley
system. The work is done in 10.0 seconds. What is the power developed in watts
and kilowatts?

3.) A person of mass 64 kg
climbs up a ladder to a height of 5.0 meters.

a.) What work does the person
do?

b.) What is the increase in the
gravitational potential energy of the

person at this height?

c.) Where does the energy come
from to cause this increase in P.E.

4.) A 60.0 kg shell is shot
from a cannon to a height of 400 meters.

a.) What is the gravitational
potential energy of the shell when it is

at this height?

b.) What is the change in
potential energy of the shell when it falls to a height of 100 meters?

5.) A person has a mass of 45
kg and is moving with a velocity of 10.0 m/s. a.) Find the personŐs kinetic
energy.

b.) The personŐs velocity
becomes 5.0 m/s. What is the kinetic energy

of the person?

c.) What is the ratio of the
kinetic energy in these two cases?

6.) A 15.0 kg object is
moving with a velocity of 17.5 m/s. A force of -50.0 N acts on the object and
its velocity becomes 3.20 m/s. What is the displacement of the object while the
force acts?

7.) What type of energy does
a wound watch spring possess? What form of energy does a running watch use?
When the watch runs down, what has happened to the energy?

8.) A 15.0 kg model plane
flies horizontally at 12.5 m/s.

a.) Calculate its kinetic
energy.

b.) The plane goes into a dive
and levels off 20.4 meters closer to the

earth. How much potential energy did it
lose during the dive?

c.) How much kinetic energy did
the plane gain during the dive?

d.) What is its new kinetic energy?

e.) Neglecting frictional
effects, what is its new horizontal velocity?

9.) A partially filled bag of
cement having a mass of 16.0 kg falls 40.0 meters into a river from a bridge.

a.) What is the kinetic energy
of of the bag as it hits the water?

b.) Using energy considerations
only, what vertical speed does it have?

10.) A 500 gram mass will
stretch a given spring 65 cm. A student replaces the 500 gram mass with a 200
gram mass. She then pulls the mass 35 cm and releases it, setting the spring into
motion.

a.) What is the spring constant
of the spring?

b.) How much work does she do in
stretching the spring?

c.) Calculate the elastic
potential energy.

d.) How fast is the mass moving
as it passes though the x = 0 position?