1
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Department of Physics
Physics 8.01 TEAL
Fall Term 2008
Exam 2 Solutions
Problem 1 (25 points). Circle your answer. There are five questions and each
question is worth 5 points.
Question A (5 points):
The figure below shows the experimental setup to study the
collision between two carts.
In the experiment cart A rolls to the right on the level track, away from the motion sensor
at the left end of the track. Cart B is initially at rest. The mass of cart A is equal to the
mass of cart B. Suppose the two carts stick together after the collision. Assume the carts
move frictionlessly.
The kinetic energy of the two carts after the collision
1)
is equal to one half the kinetic energy of cart A before the collision
2)
is equal to one quarter the kinetic energy of cart A before the collision.
3)
is equal to the kinetic energy of cart A before the collision.
4)
is equal to twice the kinetic energy of cart A before the collision.
5)
is equal to four times the kinetic energy of cart A before the collision.
6)
None of the above.
Solution (1): Since the carts stick together after the collision and they have equal
mass, the final speed of the carts is half the initial speed of cart A. The final kinetic
energy of the carts after the collision is therefore
K
f
=
1
2
(2
m
)
v
0
2
⎛
⎝
⎜
⎞
⎠
⎟
2
=
1
2
1
2
mv
A
,0
2
⎛
⎝
⎜
⎞
⎠
⎟
=
1
2
K
A
,0
(1.1)

This
** preview**
has intentionally

**sections.**

*blurred***to view the full version.**

*Sign up*