2.1 Two blocks of mass M kg and 2,5 kg respectively are connected by a light, inextensible string. The string runs over a light, frictionless pulley, as shown in the diagram below.
The blocks are stationary.
2.1.1 State Newton’s THIRD law in words. (2)
2.1.2 Calculate the tension in the string. (3)
The coefficient of static friction (μs) between the unknown mass M and the surface of the table is 0,2.
2.1.3 Calculate the minimum value of M that will prevent the blocks from moving. (5)
The block of unknown mass M is now replaced with a block of mass 5 kg. The 2,5 kg block now accelerates downwards. The coefficient of kinetic friction (μk) between the 5 kg block and the surface of the table is 0,15.
2.1.4 Calculate the magnitude of the acceleration of the 5 kg block. (5)
2.2 A small hypothetical planet X has a mass of 6,5 x 1020 kg and a radius of 550 km.
Calculate the gravitational force (weight) that planet X exerts on a 90 kg rock on this planet’s surface. (4)
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