ame: ________________________ Class: ___________________ Date: __________
ID: A
Exam 3--Fall 2009--PHYS 101
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. What happens when a spinning figure ice skater moves her arms out away from her body?
a.
b.
____
her moment of inertia increases
her moment of inertia decreases
c.
d.
her angular position remains the same
her angular velocity increases
ä×ä
B )?
2. Which of the following statements is true about the cross product (A
ä×ä
A)
I. it is equal to −(B
II. the result of the cross-product is a scalar quantity
ä or B
ä
III. the result of the cross product is orthogonal (at an angle of 90º) to either A
____
____
____
a. I
d. III
b. I & III
e. all of these are true
c. II
3. When a spinning ice skater pulls her arms in, she decreases her moment of inertia. What happens to her
rotational kinetic energy?
a. decreases
c. remains the same
b. increases
d. not enough information
4. A solid sphere and a hollow sphere have the same mass and radius. They are rotating with the same angular
speed. The one with the higher angular momentum is
a. the solid sphere
c. both the same
b. the hollow sphere
d. not enough information
5. Buckets are spinning horizontally on frictionless bearings. Suddenly, it starts raining. Which of these
statements is true:
a.
b.
the buckets’ angular speed will decrease
because their moment of inertia is
increasing
the buckets’ moment of inertia will
increase, causing the buckets angular
momentum to increase
c.
d.
1
the buckets will spin at the same angular
speed because there is no torque acting
on this
None of these are true
ame: ________________________
____
ID: A
6. When an artery becomes clogged, which of these statements describes the flow of blood through the clogged
artery?
a.
____
the velocity decreases, the pressure
c. the velocity increases, the pressure
decreases
decreases
b. the velocity decreases, the pressure
d. the velocity increases, the pressure
increases
increases
7. Two beakers are filled to the brim with water. A steel block is placed in the second beaker so it sinks to the
bottom. (Some of the water will overflow the beaker.) Both beakers are then weighed. Which scale reads a
larger weight?
____
a. beaker 1
c. both the same
b. beaker 2
8. In a mercury barometer at atmospheric pressure, the height of the column of mercury in a glass tube is 760
mm. If another mercury barometer is used that has a tube of larger diameter, how high will the column of
mercury be in this case?
____
a. higher than 760 mm
c. the same height
b. lower than 760 mm
d. not enough information
9. An ideal fluid flows through this pipe, which narrows in the middle. Because of the conservation of matter,
v2 is larger than v1. Two standpipes extend from the top of the pipe, as shown in the figure. The fluid rises
to a certain height in the standpipes. In which standpipe is the level of the fluid the highest?
a.
b.
A
B
c.
2
both the same
ame: ________________________
ID: A
____ 10. Consider this graphical representation of simple harmonic motion. When a particle is at point A, its velocity
and acceleration are...
a.
velocity and acceleration are both
d. velocity is negative and accleration is
positive
positive
b. velocity and acceleration are both
e. velocity is positive and acceleration is
positive
zero
c. velocity is positive and acceleration is
negative
____ 11. If the frequency of periodic motion increases, how is the period affected?
a. it decreases
c. it remains the same
b. it increases
d. it depends on other factors
____ 12. A mass on a spring is pulled to x=A and released. After a time of one period, what distance has the mass
travelled?
a. A
d. ¼A
b. ½A
e. 4A
c. 2A
3
ame: ________________________
ID: A
____ 13. Consider these plots of displacement versus time for an object in simple harmonic motion. How do their
periods compare?
a.
period of Object B is larger than the
c. both have the same period
period of Object A
b. period of Object A is larger than the
d. cannot tell from these graphs
period of Object B
____ 14. Consider this graphical representation of simple harmonic motion. When a particle is at point A, its position
and velocity are...
a.
b.
position is negative and velocity is
positive
position and velocity are both positive
c.
d.
4
position is positive and velocity is
negative
position and velocity are both negative
ame: ________________________
ID: A
Problem
15. (15 pts) A 60-kg swimmer climbs onto a Styrofoam block whose density is 160 kg/m 3. If the
water level comes halfway to the top of the Styrofoam, what is the block's mass?
-
5
ame: ________________________
ID: A
16. (20 pts) a) Write an expression for the position of simple harmonic motion of a mass of 20
kg on a spring with spring constant 200 N/m. The maximum velocity, which is 20 m/s, of
the spring occurs at t=2.0 seconds.
b) Calculate the period of the motion.
c) Sketch the position versus time graph for this motion.
6
ame: ________________________
ID: A
17. (15 pts) A potter's wheel, with mass of 10 kg and radius 0.3 m, is spinning freely at 22.0
radians/second. The potter drops a 2.30-kg lump of clay onto the wheel, where it sticks a
distance of 0.38 m from the rotation axis. What is the subsequent angular speed of the
wheel?
-
7
ame: ________________________
ID: A
18. (7.5 pts) Calculate the torque for a force of 3i8 + 4j8 N that acts on a moment arm of 5i8 − 2j8 m.
-
8
ame: ________________________
ID: A
19. (12.5 pts) A 0.45-kg mass on a spring is oscillating with angular frequency 7.5 rad/s and
with amplitude of 0.5 m. Derive the expression for and calculate the total energy of the
spring. (cos 2 θ + sin 2 θ = 1)
-
9
ID: A
Exam 3--Fall 2009--PHYS 101
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
A
B
B
B
A
C
B
C
A
C
A
E
B
C
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1
1
1
1
1
1
1
1
1
PROBLEM
15. ANS:
PTS: 1
16. ANS:
PTS: 1
17. ANS:
PTS: 1
18. ANS:
PTS: 1
19. ANS:
PTS: 1
1