Question 4

Two blocks, of mass 8 kg and 4 kg respectively, are joined with an inelastic string of negligible mass. The string runs over a frictionless pulley. The 8 kg block is on a horizontal surface while the 4 kg block is on an inclined plane of 40° with the horizontal. The coefficient of kinetic friction for both blocks is 0,2. The 4 kg block accelerates down the slope.

4.1 State Newton’s Second Law of Motion in words. (2)

4.2 Draw a labelled free-body diagram of ALL the forces acting on the 4 kg block. (4)

4.3 Calculate the frictional force between the surface and the 4 kg block. (4)

4.4 Calculate the magnitude of the acceleration of the system. (6)

4.5 How will the acceleration compare if the positions of the 8 kg block and 4 kg block are switched? Choose from GREATER THAN, LESS THAN or THE SAME. Explain the answer. (4)

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