1. An object falls from a great height and hits the ground. Its mass is 100 kg a

Question

1. An object falls from a great height and hits the ground. Its mass is 100 kg and it is moving at a velocity of 20 m/s upon impact. After impact

a. the earth has no added velocity

b. the earth is substantially altered in its orbit

c. the earth feels nothing at all

d. the earth has a small extra velocity to conserve momentum

2. Two balls are thrown upward. Masses are 0.1 kg and 2 kg. Right after they have left your hand, the magnitude of the acceleration of each ball is

a. 0.1 and 2

b. 10/0.1 and 2 X 0.1

c. 10/0.1 and 2/0.1

d. 10

3. A momentum change of 10 kgm/s is observed. A force of 1000N has been applied. What is the time interval that force was applied?

a. 1s

b.0.01s

c. 0.1s

d 10s

4. Momentum change of 10 kgm/s is observed. A force of 1N has been applied. For howl ong did that force act?

a. 10s

b. .01s

c. 0.1s

d. 1s

5. Cars are moving in the same direction , one at 40 mph, the other at 120 mph. They are 160 miles apart when the clock starts. The fast car is behind. When will they be next to each other?

a. 2 hr

b. 3 hr.

c. 5 hr

d. 1hr

6. A tank with a shield (10 exp 8 lbs total weight) is shown in the figure. It is motionless. A 500 lb projectile is fired with a muzzle velocity of 3000 ft/sec. It strikes the shield, does not penetrate, but fuses with it. The tank is initially motionless.

a. What is the momentum of the combination system after fusion?

b. What is the velocity of the tank immediately after the firing?

Please show work.

Explanation / Answer

1) d) since the mass of earth is so large

2) a of both is the same from gravity so d)

3) dp = F dt

so dt = dp/F = 10/1000 = 0.01

so b)

4)

dt = dp/F = 10/1 = 10 s

5)

so car 1 = 40 *t

car 2 = -160 +120*t

we want car1 = car2

40 t = - 160 + 120 t

80 t = 160

t = 2 hr so a)

6)

momemntum after = momentum before = 0

b) 0 = 10^8*v - 500*3000

v=0.015 ft/s

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