Summer Session II 2010
1
Ramp A
start
Ramp B
start
finish
finish
Introduction
In this lab you will use conservation of mechanical energy to predict the motion of objects in
situations that are difficult to analyze with force concepts.
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Prelab Activity:
Read
sections 5.3, 5.4, 5.5 & 5.6 in Serway & Faughn
1.
A skier (whose mass is 60 kg) skis down a
smooth (frictionless) ski slope, as shown in the
diagram (which is not drawn to scale).
The skier
pushes off at the top with a speed of 2.0 m/s. If
we define the absolute bottom of the slope to have zero gravitational potential energy, what
is the gravitational potential energy of the skier (in Joules) when she is at the top of the slope
(just before she pushes off)?
What is the kinetic energy of the skier (in Joules) when she
reaches a middle flat area 10 meters higher in altitude than the absolute bottom of the slope?
What is the kinetic energy of the skier (in Joules) when she reaches the absolute bottom of
the slope?
2.
A 300 gram mass is placed on a horizontal
spring.
The spring has a spring constant
k
= 650 (N/m) and is at its equilibrium length.
a)
The spring is stretched so that it is 8.0 cm
longer than its equilibrium length. How
much elastic potential energy (in Joules) is
stored in the spring now?
b)
Now the spring from part a) is released, what is speed of the mass as it passes through
the equilibrium point (
x
= 0)?
3. You release a frictionless cart at the top of each of the 2 ramps. Both carts are released from
rest. The ramps have the same height as each other at the starting and finishing points. One
has a small bump up then down just before the end. The other has a small bump down then
up. Which cart has the larger speed at the finish? Why?
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30m
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 Summer '10
 Rafaelski
 Energy, Potential Energy, CONSERVATION Summer Session, ENERGY CONSERVATION Summer

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