Question 2

A 20 kg block, resting on a rough horizontal surface, is connected to blocks P and Q by
a light inextensible string moving over a frictionless pulley. Blocks P and Q are glued
together and have a combined mass of m.

A force of 35 N is now applied to the 20 kg block at an angle of 40° with the horizontal,
as shown below.

The 20 kg block experiences a frictional force of magnitude 5 N as it moves to the
RIGHT at a CONSTANT SPEED.

2.1 Define the term normal force. (2)

2.2 Draw a labelled free-body diagram of the 20 kg block. (5)

2.3 Calculate the combined mass m of the two blocks. (5)

2.4 At a certain stage of the motion, block Q breaks off and falls down.

How will EACH of the following be affected when this happens?

2.4.1 The tension in the string
Choose from INCREASES, DECREASES or REMAINS THE SAME. (1)

2.4.2 The velocity of the 20 kg block
Explain the answer. (3)

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