Question 2

A block, of mass 8 kg, is placed on a rough horizontal surface. The 8 kg block, which is
connected to a 2 kg block by means of a light inextensible string passing over a light
frictionless pulley, starts sliding from point A, as shown below.

2.1 State Newton’s Second Law in words. (2)

2.2 Draw a labelled free-body diagram for the 8 kg block. (4)

2.3 When the 8 kg block reaches point B, the angle between the string and the
horizontal is 15° and the acceleration of the system is 1,32 m·s^-2.

2.3.1 Give a reason why the system is NOT in equilibrium. (1)

2.3.2 Use the 2 kg mass to calculate the tension in the string. (3)

2.3.3 Calculate the kinetic frictional force between the 8 kg block and the horizontal surface. (4)

2.4 As the 8 kg block moves from B to C, the kinetic frictional force between the 8 kg block and the horizontal surface is not constant.
Give a reason for this statement. (1)

The horizontal surface on which the 8 kg block is moving, is replaced by another
horizontal surface made from a different material.

2.5 Will the kinetic frictional force, calculated in QUESTION 2.3.3 above, change?
Choose from: YES or NO. Give a reason for the answer. (2)

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