PHY 131 Midterm 2
Mar 26, 2007
Version
A
Put FULL NAME, ID#, and EXAM VERSION on the front cover of the BLUE BOOKLET!
To avoid problems in grading: do all problems in order
, write legibly
, and
show all work
for partial credit
!
Note: make sketches where appropriate and show your axis conventions. Do not forget units, number of signifi
cant digits, and check your results for consistency. Do ALL problems. This exam will last 1.5 hr. Success!
1.
Ballistic pendulum
(30 points).
A mass
m=
0.500 kg (B: 1.50 kg) of putty is
thrown with horizontal velocity
v
0
=24.0 m/s perpendicular onto a vertical rec
tangular wooden board of height
H=
0.900 m (B: 0.600m), width
W=
0.500 m
(B: 0.800 m), and negligible thickness. The board has a
M=
6.00 kg mass and is
hinged at the top (A) along its width
W
. The putty smashes into the board per
pendicular to its surface at
D=
0.600 m (B: 0.400 m) below the hinge and sticks
there. For simplicity of the calculus, take
g
= 10.0 m/s
2
, and ignore friction in
the hinge and drag in the air.
Solution
a.
Calculate the angular velocity of the board plus putty just after the collision
b.
Calculate the amount of kinetic energy lost in the collision (converted to
heat)
c.
Calculate if after the collision the board will swing all the way up and around, or not. Show all work for
full credit!
2.
Torque and rotation
(35 points).
A uniform roll of paper is hung in a hinging
bracket against a vertical wall. The roll has radius
R=
0.300 m (B: 0.400 m) and
mass
M=
20.0 kg (B: 25.0 kg). The bracket has negligible mass and makes an an
gle of 45º with the wall. There is no rotational friction between the bracket and
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 Spring '03
 Rijssenbeek
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