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QUIZ 6
Physics 101, Fall 2008
November 7, 2008
Throughout the quiz, please show ALL of your work and box your answers!
Problem 1 [2 pts]. A mass attached to a spring oscillates back and forth as indicated in the
position vs. time plot below. At the point P indicated by the dot the mass has:
(Circle all correct answers!)
1.
2.
3.
4.
5.
6.
7.
8.
9.
Positive velocity and positive acceleration.
Positive velocity and negative acceleration.
Positive velocity and zero acceleration.
Negative velocity and positive acceleration.
Negative velocity and negative acceleration.
Negative velocity and zero acceleration.
Zero velocity and zero acceleration.
The sign of the velocity is indeterminant.
The sign of the acceleration is indeterminant.
Problem 2 [2 pts]. A girl swings on a swing. When the girl sits still, the swing oscillates back
and forth at its natural frequency. If, instead, the girl stands on the swing in such a way that her
center of mass is always directly between her feet and the pivot, the new natural frequency of the
swing is:
(Circle all correct answers!)
1.
2.
3.
4.
Greater.
The same.
Smaller.
There is no sufficient information to answer.
Problem 3. A sliding block of mass M =3.21 kg is attached to the end of a spring with constant
k=105 N/m. The second end of the spring is attached to a wall. The block slides on a frictionless
surface. When the block crosses the rest position of the spring, its speed v reaches the maximum
value of 12.3 m/s. See also the figure below, where the block is shown in the point of the trajectory
where the spring is maximally compressed.
rest
position
k
y
M
x
QUIZ 6
Physics 101, Fall 2008
November 7, 2008
a. [1 pts] What is the angular frequency of the oscillations?
b. [2 pts] What is the maximum distance by which the spring is compressed? Note: this is
equivalent to the amplitude A of the oscillations.
c. [3 pts] A bullet of mass m=0.010 kg is shot from left to right and collides with the block at the
moment the spring is maximally compressed. The bullet has a velocity vb =1250 m/s prior to the
collision and gets stuck into the block after the collision. What is the amplitude B of the oscillations
after the collision?
rest
position
k
vb
y
x
m
M
Rewrite and sign the pledge: I pledge my honor that I have not violated the Honor Code during this
examination.
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