Physics

————————————————————————————————–
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) During a collision with a wall, the velocity of a 0.200-kg ball changes from 20.0 m/s toward the wall
to 12.0 m/s away from the wall. If the time the ball was in contact with the wall was 60.0 ms, what
was the magnitude of the average force applied to the ball?
A) 26.7 N B) 16.7 N C) 40.0 N D) 107 N E) 13.3 N
1)
2) A stationary 1.67-kg object is struck by a stick. The object experiences a horizontal force given by F
= at – bt2, where t is the time in milliseconds from the instant the stick first contacts the object. If a =
1500 N/(ms) and b = 20 N/(ms)2, what is the speed of the object just after it comes away from the
stick at t = 2.74 ms?
A) 25 m/s B) 3.3 m/s C) 3.7 m/s D) 22 m/s
2)
3) A batter hits a foul ball. The 0.14-kg baseball that was approaching him at 40 m/s leaves the bat at
30 m/s in a direction perpendicular to the line between the batter and the pitcher. What is the
magnitude of the impulse delivered to the baseball?
A) 1.4 N · s B) 7.0 N · s C) 9.8 N · s D) 5.6 N · s E) 3.5 N · s
3)
4) A 620-g object traveling at 2.1 m/s collides head-on with a 320-g object traveling in the opposite
direction at 3.8 m/s. If the collision is perfectly elastic, what is the change in the kinetic energy of the
620-g object?
A) It loses 1.4 J.
B) It loses 0.23 J.
C) It gains 0.69 J.
D) It loses 0.47 J.
E) It doesn’t lose any kinetic energy because the collision is elastic.
4)
5) A block of mass m = 34 kg and speed V is behind a block of mass M = 81 kg and speed of 0.50 m/s,
as shown in the figure. The surface is frictionless and the blocks collide and couple. After the
collision, the blocks have a common speed of 0.90 m/s. What is the magnitude of the impulse on the
34-kg block due to the collision?
A) 41 N · s B) 32 N · s C) 57 N · s D) 73 N · s E) 14 N · s
5)
6) A 2.3-kg object traveling at 6.1 m/s collides head-on with a 3.5-kg object traveling in the opposite
direction at 4.8 m/s. If the collision is perfectly elastic, what is the final speed of the 2.3-kg object?
A) 4.3 m/s B) 7.1 m/s C) 3.8 m/s D) 0.48 m/s E) 6.6 m/s
6)
7) A 1500-kg car traveling at 90 km/h toward the east suddenly collides with a 3000-kg car traveling
at 60 km/h toward the south. The two cars stick together after the collision. What is the direction of
motion of the cars after collision?
A) 53.1° S of E B) 53.1° E of S C) 36.9° S of E D) 36.9° E of S
7)
1
8) Three objects are moving along a straight line as shown in the figure. Taking the positive direction
to be to the right, what is the total momentum of this system?
A) +14.0 kg · m/s
B) +106 kg · m/s
C) 0.00 kg · m/s
D) -106 kg · m/s
E) -14.0 kg · m/s
8)
9) A block of mass m = 8.40 kg, moving on a horizontal frictionless surface with a speed 4.20 m/s,
makes a perfectly elastic collision with a block of mass M at rest. After the collision, the 8.40 block
recoils with a speed of 0.400 m/s. In the figure, the blocks are in contact for 0.200 s. The magnitude
of the average force on the 8.40-kg block, while the two blocks are in contact, is closest to
A) 185 N B) 160 N C) 168 N D) 193 N E) 176 N
9)
10) A billiard ball traveling at 3.00 m/s collides perfectly elastically with an identical billiard ball
initially at rest on the level table. The initially moving billiard ball deflects 30.0° from its original
direction. What is the speed of the initially stationary billiard ball after the collision?
A) 2.00 m/s B) 0.750 m/s C) 0.866 m/s D) 2.59 m/s E) 1.50 m/s
10)
11) A 480-kg car moving at 14.4 m/s hits from behind a 570-kg car moving at 13.3 m/s in the same
direction. If the new speed of the heavier car is 14.0 m/s, what is the speed of the lighter car after
the collision, assuming that any unbalanced forces on the system are negligibly small?
A) 19.9 m/s B) 5.24 m/s C) 13.6 m/s D) 10.5 m/s
11)
2
12) A 15-g bullet is shot vertically into an 2-kg block. The block lifts upward 8.0 mm (see the figure).
The bullet penetrates the block and comes to rest in it in a time interval of 0.0010 s. Assume the
force on the bullet is constant during penetration and that air resistance is negligible. The initial
kinetic energy of the bullet is closest to
A) 10 J B) 0.16 J C) 14 J D) 0.0012 J E) 21 J
12)
13) An 8.0-g bullet is shot into a 4.0-kg block, at rest on a frictionless horizontal surface (see the figure).
The bullet remains lodged in the block. The block moves into an ideal massless spring and
compresses it by 8.7 cm. The spring constant of the spring is 2400 N/m. The initial velocity of the
bullet is closest to
A) 1300 m/s. B) 1000 m/s. C) 1200 m/s. D) 1100 m/s. E) 900 m/s.
13)
14) Two automobiles traveling at right angles to each other collide and stick together. Car A has a mass
of 1200 kg and had a speed of 25 m/s before the collision. Car B has a mass of 1600 kg. The skid
marks show that, immediately after the collision, the wreckage was moving in a direction making
an angle of 40° with the original direction of car A. What was the speed of car B before the collision,
assuming that any other unbalanced forces are negligible?
A) 16 m/s B) 21 m/s C) 14 m/s D) 11 m/s E) 18 m/s
14)
15) Two ice skaters push off against one another starting from a stationary position. The 45.0-kg skater
acquires a speed of 0.375 m/s. What speed does the 60.0-kg skater acquire? Assume that any other
unbalanced forces during the collision are negligible.
A) 0.281 m/s B) 0.500 m/s C) 0.750 m/s D) 0.000 m/s E) 0.375 m/s
15)
3
Answer Key
Testname: PHYS 211 – H8
1) D
2) B
3) B
4) B
5) B
6) B
7) A
8) E
9) D
10) E
11) C
12) E
13) D
14) A
15) A
4