If a 3 kg ball is dropped from a height of 33 meters, what will its kinetic energy be just
before landing? (show calculations using work/energy equations.) (2 pts)
For this question, we know that there is no potential energy right before the ball lands, because
all of the energy is kinetic energy. But, the conservation of momentum law states that energy is
always conserved, so in this case, the change in Potential Energy from the peak to the bottom
will be equal to the change in Kinetic Energy, PE (initial)= KE (final), giving us the kinetic
energy of the ball before landing. So we have PE = mgh PE = 9.81(33)(3kg) = 971.2 J So the
ball has a Kinetic Energy of 971.2 J just before landing.
Or you could use projectile equations to calculate the velocity of landing and calculate the
energy that we.
v
f
2
= v
i
2
+ 2g Dy
vf=25.45 m/s
K=1/2mv
2
K=971 J
If a 3 kg ball is dropped from a height of 33 meters, how fast will it be traveling just before
landing? (2 pts)
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 Summer '11
 STAFF
 Energy, Kinetic Energy, Mass, Potential Energy, Velocity, kg ball

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