# A2L Item 280

Goal: Unspecified.

Source: Unspecified.

A student suggests that an unknown mass can be measured by placing a known mass on a frictionless incline and measuring the acceleration. Then place the unknown mass on the same incline and measure the acceleration. From this information you can find the value of the new mass. Will this work? Be prepared to explain.

1. Yes
2. No

None provided.

# A2L Item 278

Goal: Unspecified.

Source: Unspecified.

When a force F is applied to a mass of 2 kg, the mass accelerates with 6.3 m/s2. When the same force is applied to an unknown mass the acceleration is 9 m/s2. Assume no friction. The value of the mass is:

1. 0.3 kg
2. 0.7 kg
3. 1.2 kg
4. 4.5 kg
5. 14 kg
6. None of above.

None provided.

# A2L Item 279

Goal: Unspecified.

Source: Unspecified.

An applied force FA pushes a block of mass m up a rough incline having coefficient of kinetic friction μk. The friction force on the block is:

1. mgcosθ
2. mgsinθ
3. μkmgsinθ
4. μkmgcosθ
5. μkmgtanθ
6. μkmgsinθcosθ
7. None of the above.
8. Can’t be determined.

None provided.

# A2L Item 276

Goal: Unspecified.

Source: Unspecified.

A pendulum is released from rest at position A and swings toward the
vertical under the influence of gravity as depicted below.

When at position B, which direction most nearly corresponds to the
direction of the acceleration?

Enter (9) if the direction cannot be determined.

None provided.

# A2L Item 275

Goal: Unspecified.

Source: Unspecified.

Two cars have a race. Car A drives with constant speed of 20 m/s. Car B
drives with speed 10 m/s for 3 s, then accelerates uniformly to a speed
of 25 m/s during the next 3 s. Car B maintains the speed of 25 m/s for
the rest of the race.

What is the minimum length of race if Car B is to overtake car A?

None provided.

# A2L Item 274

Goal: Unspecified.

Source: Unspecified.

Two cars have a race. Car A drives with constant speed of 20 m/s. Car B
drives with speed 10 m/s for 3 s, then accelerates uniformly to a speed
of 25 m/s during the next 3 s. Car B maintains the speed of 25 m/s for
the rest of the race.

If the race is very long, can car B ever catch car A?

1. YES
2. NO
3. Not enough information.

None provided.

# A2L Item 273

Goal: Unspecified.

Source: Unspecified.

Jane is riding in a hot air balloon that is rising vertically at a
constant speed of 3 m/s over a lake. She reaches out and drops a rock
from the balloon when the distance from the rock to the water is 50 m.
Use g=10 m/s2, and let the up direction be positive. About
how long after Jane drops the rock will it splash into the water?

1. 2.0 sec
2. 2.6 sec
3. 3.5 sec
4. 5.0 sec
5. 6.8 sec
6. 8 sec

None provided.

# A2L Item 271

Goal: Unspecified.

Source: Unspecified.

Jane is riding in a hot air balloon that is rising vertically at a
constant speed of 3 m/s over a lake. She drops a rock from the balloon
when the distance from the rock to the water is 50 m. Use g=10
m/s2, and let up be the positive direction. What is the
initial velocity of the rock?

1. 3 m/s
2. -3 m/s
3. 0
4. Cannot be determined.
5. None of the above.

None provided.

# A2L Item 272

Goal: Unspecified.

Source: Unspecified.

Jane is riding in a hot air balloon that is rising vertically at a
constant speed of 3 m/s over a lake. She drops a rock from the balloon
when the distance from the rock to the water is 50 m. Use g=10
m/s2, and let up be the positive direction. Assume the origin
is on the surface of the water, what is the initial position of the
rock?

1. 0
2. 50 m
3. -50 m
4. None of the above.

None provided.