Chapter Pretests


Chapter 6 Quiz
 
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Chapter 6 Quiz


Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 1. 
A miniature spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 5.00 g, and the gun and puck have a combined mass of 120 g. With the system initially at rest, the radio controlled trigger releases the bullet causing the puck and empty gun to move with a speed of 0.500 m/s. What is the bullet's speed?
a.
23.0 m/s
b.
11.5 m/s
c.
12.0 m/s
d.
4.80 m/s
e.
48.0 m/s
 

 2. 
A crane drops a 0.30 kg steel ball onto a steel plate. The ball's speeds just before impact and after are 4.5 m/s and 4.2 m/s, respectively. If the ball is in contact with the plate for 0.030 s, what is the magnitude of the average force that the ball exerts on the plate during impact?
a.
87 N
b.
3.0 N
c.
133 N
d.
60 N
e.
3.5 N
 

 3. 
A tennis ball is held above and in contact with a basketball, and then both are simultaneously dropped. The tennis ball bounces off the basketball at a fairly high speed. This is because:
a.
the massive basketball transfers momentum to the lighter tennis ball.
b.
the tennis ball has a smaller radius.
c.
the tennis ball is slightly shielded from the Earth's gravitational pull.
d.
the basketball falls farther than the tennis ball.
e.
None of the above choices are valid.
 

 4. 
An object of mass m moving at speed v0 strikes and object of mass 2m which had been at rest. The first object bounces backward along its initial path at speed v0. Is this collision elastic, and if not, what is the change in kinetic energy of the system?
a.
The kinetic energy decreases by mc004-1.jpgmv2.
b.
The kinetic energy increases by mv2.
c.
The kinetic energy decreases by mv2.
d.
The collision is elastic.
e.
The kinetic energy increases by mc004-2.jpgmv2.
 

 5. 
A moderate force will break an egg. However, an egg dropped on the road usually breaks, while one dropped on the grass usually doesn't break. This is because for the egg dropped on the grass:
a.
the change in momentum is greater.
b.
the change in momentum is less.
c.
the time interval for stopping is greater.
d.
the time interval for stopping is less.
e.
Both choices A and C are valid.
 

 6. 
Two identical 7-kg bowling balls roll toward each other. The one on the left is moving at +4 m/s while the one on the right is moving at -4 m/s. What is the velocity of each ball after they collide elastically?
a.
Neither is moving.
b.
-14 m/s, 14 m/s
c.
+14 m/s, -14 m/s
d.
-4 m/s, +4 m/s
e.
+4 m/s, -4 m/s
 

 7. 
If a two-body collision is not head-on, then we may always assume that:
a.
momentum is conserved.
b.
neither momentum nor kinetic energy are conserved.
c.
kinetic energy is conserved.
d.
both momentum and kinetic energy are conserved.
e.
none of the above choices are valid.
 

 8. 
A 75-kg swimmer dives horizontally off a 500-kg raft. If the diver's speed immediately after leaving the raft is 4 m/s, what is the corresponding raft speed?
a.
0.2 m/s
b.
4.0 m/s
c.
0.5 m/s
d.
0.6 m/s
e.
5.0 m/s
 

 9. 
During a snowball fight two balls with masses of 0.4 and 0.6 kg, respectively, are thrown in such a manner that they meet head-on and combine to form a single mass. The magnitude of initial velocity for each is 15 m/s. What is the speed of the 1.0-kg mass immediately after collision?
a.
6 m/s
b.
10 m/s
c.
9 m/s
d.
zero
e.
3 m/s
 

 10. 
A 1 000-kg experimental rocket sled on level frictionless rails is loaded with 50 kg of propellant. It exhausts the propellant in a 20-s "burn." If the rocket, initially at rest, moves at 150 m/s after the burn, what impulse is experienced by the rocket sled?
a.
1.1 ´ 105 kg×m/s
b.
2.1 ´ 105 kg×m/s
c.
1.5 ´ 105 kg×m/s
d.
1.9 ´ 105 kg×m/s
e.
1.6 ´ 105 kg×m/s
 

 11. 
Jerome pitches a baseball of mass 0.20 kg. The ball arrives at home plate with a speed of 40 m/s and is batted straight back to Jerome with a return speed of 60 m/s. What is the magnitude of change in the ball's momentum?
a.
4.0 kg×m/s
b.
24 kg×m/s
c.
18 kg×m/s
d.
8.0 kg×m/s
e.
20 kg×m/s
 

 12. 
Kaitlin uses a bat to hit a thrown baseball. She knocks the ball back in the direction from which it came in a partially inelastic collision. The bat, which is heavier than the baseball, continues to move in the same direction after the hit as Kaitlin "follows through." Is the ball moving faster before or after it was hit?
a.
The ball was moving at essentially the same speed before and after the hit.
b.
The ball was moving faster after it was hit.
c.
The ball was moving faster before it was hit.
d.
There is insufficient information to answer this problem.
 

 13. 
Two objects, one less massive than the other, collide elastically and bounce back after the collision. If the two originally had velocities that were equal in size but opposite in direction, then which one will be moving faster after the collision?
a.
The more massive one.
b.
There is no way to be sure without the actual masses.
c.
The less massive one.
d.
The speeds will be the same after the collision.
 

 14. 
A 70-kg man is standing in a 20-kg boat. The man steps to the right thinking he is stepping out onto the dock. However, the following will actually happen (ignore the friction of the water or air on the boat or the man):
a.
The boat doesn't move and the man moves to the right.
b.
The boat and the man don't move.
c.
The man actually stays still while the boat moves toward the left.
d.
The man only moves a short distance to the right while the boat moves a larger distance to the left.
e.
None of the above.
 

 15. 
A helicopter stays aloft by pushing large quantities of air downward every second. What mass of air must be pushed downward at 40.0 m/s every second to keep a 1 000-kg helicopter aloft?
a.
120 kg
b.
520 kg
c.
245 kg
d.
490 kg
e.
360 kg
 

 16. 
Alex throws a 0.15-kg rubber ball down onto the floor. The ball's speed just before impact is 6.5 m/s, and just after is 3.5 m/s. What is the change in the magnitude of the ball's momentum?
a.
126 kg×m/s
b.
0.09 kg×m/s
c.
4.3 kg×m/s
d.
5.7 kg×m/s
e.
1.5 kg×m/s
 

 17. 
A valid unit for momentum is which of the following?
a.
kg×m/s
b.
kg/m2
c.
N×m
d.
kg×m/s2
e.
N/m
 

 18. 
A uranium nucleus (mass 238 units) at rest decays into a helium nucleus (mass 4.0 units) and a thorium nucleus (mass 234 units). If the speed of the helium nucleus is 6.0 ´ 105 m/s, what is the speed of the thorium nucleus?
a.
4.1 ´ 104 m/s
b.
3.6 ´ 104 m/s
c.
4.8 ´ 104 m/s
d.
3.0 ´ 104 m/s
e.
1.0 ´ 104 m/s
 

 19. 
Popeye, of mass 70 kg, has just downed a can of spinach. He accelerates quickly and stops Bluto, of mass 700 kg (Bluto is very dense), who is charging in at 10 m/s. What was Popeye's speed?
a.
50 m/s
b.
31 m/s
c.
100 m/s
d.
120 m/s
e.
10 m/s
 

 20. 
A 1 000-kg experimental rocket sled at rest on level frictionless rails is loaded with 50 kg of propellant. It exhausts the propellant in a 20-s "burn." The rocket moves at 150 m/s after the burn. What average force is experienced by the rocket during the burn?
a.
0.95 ´ 104 N
b.
0.35 ´ 104 N
c.
0.60 ´ 104 N
d.
0.75 ´ 104 N
e.
0.25 ´ 104 N
 



 
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