5. Suppose that two blocks on a table are pulled to the left by a horizontal 5 puan force of 5 N. Both boxes move together at a constant speed. Which of the following statement(s) is/are true? I. Acceleration of the blocks is zero. II. The net force on the system of the two blocks is zero. III. The frictional force that the surface of the table exerts on the block A is 5 N. IV. The friction force that blok A exerts on the block B is in the direction to the left. 2.0 kg В F = 5N 5.0 kg A Only Il and II Only II, III, and IV Only I and II Only I and III Only I, Il and II I, II, III, and IV

2. Imagine you are trying to move a very heavy box, and it does not move. Then, you get a friend to help you push and it begins to slide. Explain, in terms of the quantities discussed in this investigation (Fk, тах Hs,Fk9 Hk) what is happening to the box in these two cases.

A 4.0 kg mass moving at 2 m/s and a 2 kg mass moving at 4 m/s are gliding over a frictionless surface. Both objects encounter the same horizontal force, which directly opposed their motion and are brought to rest. Which statement correctly describes the situation? a. The 2.0 kg mass travels twice as far as the 4.0 kg mass before stopping. b. The 2.0 kg mass travels farther but necessarily twice as far. c. The 4.0 kg mass travels twice as far as the 2.0 kg mass before stopping. d. The 4.0 kg mass loses more kinetic energy than the 2.0 kg mass. e. Both masses travel the same distance before stopping.

2. Take the example in class for when a fan attached to the sailboat fails to move the boat forward. The sail is removed but the fan keeps running. Will the boat move then? Why or why not? If so, which way will the boat move?

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