ame: ________________________
Exam 2--PHYS 201--F10
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
____
____
1. Which of these statements about projectile motion is true:
a. The y-component of the velocity is zero at the top of the trajectory
b. The acceleration in the y-direction is 0.
c. The x-component of the velocity is largest at the beginning of the motion
d. The y-component of the velocity is constant
2. You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the
package will:
a. move ahead of the plane while falling
b. not fall at all
c. quickly lag behind the plane while falling
d. remain vertically under the plane while falling
3. Which of these punts has the longest hang time?
a.
b.
a
b
c.
d.
1
c
all the same
____
4. This figure shows an inclined plane with a block; the block is accelerating up the inclined plane. The 3
ä--are labeled. Which of the following is an appropriate
forces--normal force, weight, and an applied force F
equation that follows from the application of Newton’s second law of motion?
a.
b.
____
____
c.
d.
ä sin60 o = F
ä
F
w
ä
ä
F =F
w
5. Antilock breaks keep the car wheels from locking up when you stop your car. Why does this help slow the
car down?
a.
b.
____
ä −F
ä=0
F
ä
F − ä
F w sin30 o = ma x
µk > µs so static friction is better
µs > µk so sliding friction is better
c.
d.
µk > µs so sliding friction is better
µs > µk so static friction is better
6. A cart is on a horizontal frictionless table. Once the cart has been pushed and released, what will happen to
it?
a. it will immediately come to a stop
c. it will gradually slow down
b. it will continue at constant velocity
d. it will continue at constant acceleration
7. A block of mass m rests on the floor of an elevator that is accelerating upward at 12 m/s 2. What is the
relationship between the force due to gravity (mg) and the normal force (N) on the block?
a. N=mg
d. N=0
b. N<mg
e. depends on the speed of the elevator
c. N>mg
2
____
____
8. A box is being pulled across a rough floor at a constant speed. What can you say about the work done by
friction?
a. friction does negative work
c. friction does no work
b. friction does positive work
9. A ball tied to a string is being whirled around in a circle. What can you say about the work done by tension?
a. tension does positive work
c. tension does no work
b. tension does negative work
____ 10. A car starts from rest and accelerates to 30 mph. Later, it gets on a highway and accelerates to 60 mph.
Which takes more energy, the 0⇒30 mph, or the 30⇒60 mph?
c. each requires the same energy
a. 0⇒30 mph
b. not enough information to tell
d. 30⇒60 mph
____ 11. Which of these is best approximated as an inelastic collision?
I. Collision of two cars
II. Collision between particles of gas
III. Collision between baseball & bat
a. I
d. II
b. II & III
e. None of these
c. I & III
____ 12. A collection of particles has a total kinetic energy of zero. What can we say about the momentum of the
system?
a.
the momentum is positive
d.
b.
c.
the momentum is negative
the momentum is zero
e.
3
the momentum is either positive or
negative, but not zero
not enough information
____ 13. A uranium nucleus is at rest and undergoes fission and splits into two fragments, one heavy and one light.
Which of these statements is true?
a.
the lighter fragment has more momentum c.
than the heavier fragment
b. the heavier fragment has more
d.
momentum than the lighter fragment
____ 14. Complete this statement.
the lighter fragment has a higher speed
than the heavier fragment
both particles have the same speed
A net force of 300 N acts on a 200-kg boulder, and a force of the same magnitude acts on a 120-g pebble.
The rate of change of the boulder’s momentum is...
a. equal to the rate of change of the pebble’s momentum
b. greater than the rate of change of the pebble’s momentum
c. less than the rate of change of the pebble’s momentum
____ 15. Amy (100 lbs) and Gwen (50 lbs) are standing on slippery ice and push off each other. If Amy slides at 4
m/s, what speed does Gwen have?
a.
b.
6 m/s
8 m/s
c.
d.
4
2 m/s
4 m/s
Problem
16.
(20 pts) Consider this figure. The coefficient of kinetic
friction between the inclined plane and the block is µk=0.1.
If the right-hand mass is m2=4 kg, what should m1 be so that
(a) it accelerates downslope at 2 m/s2?
5
17.
(10 pts) A force F = 40i + 20j + 60k N is applied to a body as
it moves in a straight line from r1= 16i +3j; to r2 = 32i + 10j 12k m. How much work is done by the force?
.
6
18.
(15 pts) A force given by the equation below acts in the x
direction. Calculate the work done by this force acting on an
object as it moves from x = -2 to x = 4 m.
F = 2x
1
2
.
7
19.
(10 pts) A particle slides along the frictionless track shown in
this figure. At point A, the particle has a speed of 3 m/s. Find
(a) its speed at C and (b) the approximate location of its
right-hand turning point.
8
20.
(15 pts) A 1000-kg compact car is moving with velocity v1 =
20i + 40j m/s. It skids on a frictionless icy patch and collides
with a 500-kg hay wagon moving with velocity v2 = 10i - 5j
m/s. If the two stay together, what is their velocity, in vector
notation?
.
9
ID: A
Exam 2--PHYS 201--F10
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
CT
A
D
D
C
D
B
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1
1
1
PTS: 1
7. ANS: C
CT
8.
9.
10.
11.
12.
13.
14.
15.
PTS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
1
A
C
D
C
C
C
A
B
PROBLEM
16. ANS:
.
PTS: 1
17. ANS:
.
PTS: 1
18. ANS:
.
PTS: 1
19. ANS:
.
PTS: 1
1
ID: A
20. ANS:
.
PTS: 1
2