Question 4

4.1 In the diagram below, a 2 kg block is connected to a 1 kg block by means of a
light inextensible string. The blocks are pulled up an inclined plane, which
forms an angle of 28^o to the horizontal. The sides of the blocks which touch
the inclined plane have the same area.

The kinetic frictional force between the 1 kg block and the inclined plane is
4 N while the kinetic frictional force between the 2 kg block and the inclined
plane is 8 N.

4.1.1 Draw a labelled free-body diagram showing ALL the forces acting
on the 1 kg block. (5)

4.1.2 State Newton’s second law of motion in words. (2)

4.1.3 Calculate the magnitude of the tension in the string connecting the
blocks. (5)

The two blocks are interchanged so that the SAME 30 N force is now acting
on the 2 kg block along the inclined plane, as shown in the diagram below.

4.1.4 How will the acceleration of the system change? Write down only
INCREASE, DECREASE or REMAIN THE SAME. (1)

4.1.5 How will the tension in the string connecting the two blocks
change? Write down only INCREASE, DECREASE or REMAIN
THE SAME. (1)

4.2 In the diagram below, a 1 kg mass and a 2 kg mass are connected by an
inextensible string of negligible mass. The string is passed over a light
frictionless pulley so that the masses hang down as shown. Initially the
system is held stationary.

4.2.1 Draw a labelled free-body diagram showing ALL the forces acting on
the 2 kg mass. (2)

4.2.2 Calculate the time it will take the 1 kg mass to move a distance of 1 m
when the system is released. (2)

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