Download Back Questions on Momentum

Back Questions on Momentum
1.
A baseball moves towards a batter at 30 m/s. The batter hits the ball back towards the pitcher
at 40 m/s. If the baseball has a mass of 0.020 grams, and the bat is in contact with the ball
for 0.030 seconds, then the force of the bat on the ball was most nearly
a) 333 N
2.
c) Work
d) Moment of Inertia
b) 2 M
c) ½ M
d) TINEI
make the time that the “slow–down” force is in contact with the object as long as possible.
make the time that the “slow–down” force is in contact with the object as short as possible.
reduce the kinetic energy of the object to zero as quickly as possible.
do positive work on the object.
A 500 kg car moving at 30 m/s to the right collides with, and sticks to, a 400 kg car moving
at 20 m/s to the left. After the collision, what is the velocity of the tangled mess of cars?
a) 7.78 m/s left
b) 7.78 m/s right
6.
b) Momentum
It is often desired to take a fragile, moving object (like your head) and reduce its speed to zero.
If we want to do this with the least nasty effect on the moving object we should
a)
b)
c)
d)
5.
d) 46.7 N
A mass M is moving to the right at a speed V; it collides head–on with a mass moving at speed
2V to the left. After they collide, and stick together, the combined masses are at rest. What is
the mass of the object moving to the left, in terms of the mass moving to the right?
a) M
4.
c) 6.67 N
The product of the sum of a forces on an object and the time for which that sum works on the
object is called . . .
a) Impulse.
3.
b) 2333 N
c) 25.6 m/s left
d) 25.6 m/s right
If, in question 5, we did not know the original velocity of the 400 kg car, but we observed that
after the collision the tangled mess was at rest, then we could conclude
a)
b)
c)
d)
that the 400 kg car was originally moving at 37.5 m/s to the right.
that the 400 kg car was originally moving at 37.5 m/s to the left.
that the 400 kg car was originally at rest.
nothing; we do not have enough information.
7.
In order for linear momentum to be conserved,
a) Fext = 0
b) ext = 0
8.
c) either (a) or (b).
d) both (a) and (b).
e) neither (a) nor (b).
A 10,000 kg truck moving to the right at 15 m/s collides and becomes entangled with a car that
is moving to the left at 40 m/s. The car has a mass of 3000 kg, and the collision is head on.
After the collision, the tangled mess is moving
a) to the right at 2.31 m/s.
b) to the left at 2.31 m/s.
c) to the right at 20.8 m/s.
d) to the left at 20.8 m/s.
If, in question #8, we don’t actually know the speed of the car, but we do know that the
tangled mess actually came to rest after the collision, we can deduce that the car was initially
9.
a) at rest.
b) moving to the left at 40 m/s.
c) moving to the left at 50 m/s.
d) We cannot deduce anything.
An object’s momentum changes by an amount p  pf  pi. In order to minimize the force
necessary to cause this change, we should try to
10.
a)
b)
c)
d)
11.
make the time that the force is in contact with the object as small as possible.
make the time that the force is in contact with the object as large as possible.
make the force causing the change perpendicular to the direction pi.
make the force causing the change perpendicular to the direction pf.
When a very large object is hit by a smaller object, and the smaller object stops but the larger
object does not start moving, the larger object is said to _________ momentum.
a) conserve
b) absorb
c) repel
d) deflect
Which of Newton’s laws of motion is most directly related to the law of conservation of
momentum?
12.
a)
The first law
b) The second law
c) The third law
d) The fourth law
Answers:
1.
D
2: A
3: C
4: A
5: B
6: B
7. A
8: A
9: C
10: B
11: B
12: C