Physics 1A
ENERGY & ENERGY CONSERVATION
Fall 2009
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.
_____________________________________________________________________________
Prelab Activity:
1.
A skier (whose mass is 65 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 5.0 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 the absolute bottom of the slope?
2.
A 250 gram mass is placed on a horizontal
spring.
The spring has a spring constant
k
= 590 (N/m) and is at its equilibrium length.
a)
The spring is stretched so that it is 7.5 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. On Ramp B, the cart is
released from rest, but on Ramp A the cart is pushed at the top so that it has some initial
velocity. 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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 Spring '11
 lee
 Energy, Potential Energy

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