Download Potential and Kinetic Energy Practice

Potential and Kinetic Energy Practice
1. Milford was cracking nuts on his 6th floor balcony when the 160-kg
anvil he was using slipped and fell to the ground. The balcony is 20 m
above ground level. This was not the first time Milford’s anvil had
gone astray, so a special sign was posted along the sidewalk below.
A. What was the potential energy of the anvil on the balcony?
B. What was the kinetic energy of the anvil just before it hit the ground?
C. What was the speed of the anvil just before it hit the ground?
D. What was the speed of the anvil when it was 10 m above the ground?
E. How much work did Milford have to do to carry the anvil back up to his 6th floor
balcony?
Useful Formulas
KE = ½mv2
F. If it took Milford 10 minutes to carry the anvil
back up to his balcony, what was the average
v=
power expended?
PE = mgh
2xKE
m
W = Fd
W = mgh (lifting)
P
W
t
h 
KE
mg
2. An astronaut is hovering 1000 m above the surface of the Moon
when her rocket transport runs out of fuel. She decides to bail out
and parachute to the surface before she remembers the Moon has
no atmosphere. The acceleration due to gravity on the Moon is
gMoon = 1.6 m/s2. The astronaut (with space suit) has a mass of 140
kg.
A. What is the astronaut’s potential energy at 1000 m?
B. With what speed does the astronaut hit the surface?
3. A rammer is a round piece of wood which serves to drive home the powder and ball to
the breech of the cannon. It is fastened to a stick that can be up to twelve feet long.
After preparing the cannon for the next
shot and lighting the fuse, a member of the
artillery crew responsible for handling the
rammer tripped and fell onto the cannon,
knocking it so that it pointed straight up. A few seconds later the cannon went off,
sending the 10-kg cannonball skyward at a velocity of 100 m/s.
A. How long does it take the cannonball to
reach its highest point? (Hint: Remember
that g = 10 m/s/s)
B. Using Conservation of Energy, what is the
maximum height the cannonball reaches?