1. 100 N, to the left
2. 10 N, to the left
3. 5 N, to the left
4. 10 N, to the right
5. 5 N, to the right

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Question 5.1

A wooden block has a mass of 10.2 kg, so the force of gravity of the Earth on the block is 100 N. The block is supported by a smooth horizontal concrete surface. The coefficient of kinetic friction between wood and concrete is 0.1.

A 5 N horizontal force is applied to the block, pushing it toward the right.

At this instant of time, the block is sliding to the right at a speed of 5 m/s.

What is the force of kinetic friction of the surface on the block?

• A car is parked on flat, horizontal pavement.
• Which of the following forces should be added to the force diagram of the car?
• [Choose all the non-zero forces below.]
• Weight of the Car
• Normal force of surface on car
• Static friction of surface on car

Question 5.2

A wooden block has a mass of 10.2 kg, so the force of gravity of the Earth on the block is 100 N. . The block is supported by a smooth horizontal concrete surface. The coefficient of static friction between wood and concrete is 0.2.

A 5 N horizontal force is applied to the block, pushing toward the right, but the block does not move. What is the force of static friction of the surface on the block?

1. 100 N, to the left
2. 20 N, to the left
3. 5 N, to the left
4. 20 N, to the right
5. 5 N, to the right

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Question 5.3

A wooden block has a mass of 10.2 kg, so the force of gravity of the Earth on the block is 100 N. The block is sitting stationary on a smooth horizontal concrete surface. The coefficient of static friction between wood and concrete is 0.2.

What is the magnitude of the maximum horizontal force you can exert on the block and have the block remain stationary?

1. 200 N
2. 100 N
3. 20 N
4. 10 N
5. 5 N

Question 5.4

A crate is pushed with 3 different forces in 3 different cases, shown. The crate always has the same mass. In all three cases, the create is in equilibrium (no acceleration). In which case is the magnitude of the friction force of the floor on the crate the greatest?

1. A
2. B
3. C
4. The magnitude of the foce of the the floor on the crate is the same in all three cases.

Question 5.5

An empty box is on an incline, and it doesn’t slip.

What happens if you keep adding rocks to the box, but keep the angle fixed?

1. It eventually slips
2. It doesn’t slip
3. It depends on the angle

Question 5.6

Question 5.7

Three parachutists, A, B and C, each have reached terminal velocity. Which one is falling fastest?

4. All three are falling at the same speed.

Question 5.8

Which falls faster, large raindrops or small raindrops?

1. Large
2. Small
3. No difference

Question 5.9

• A wire has a length of 1.00 m.
• When a 1 kg mass is suspended from the bottom of the wire, it stretches to a new length of 1.01 m.
• If, instead, a 3 kg mass were suspended from the same wire, what would its length be?
• 1.01 m
• 1.03 m
• 3.00 m
• 3.03 m