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# Friction

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1.
a) A block with a mass m is pulled along a horizontal surface for a distance +x by a constant force F at an angle theta with respect to the horizontal. The coefficient of kinetic friction between block and table is µ. Is the force exerted by friction equal to µmg?

b) How much work is done by the friction force and by F?

c) Identify all the forces that do no work on the block.

d) Let m = 2.00 kg, x = 4.40 m, theta = 46.0°, F = 14.0 N, and µ = 0.4, and find the answers to parts (a) and (b).

2.
A 2.00 kg block situated on a rough incline is connected to a spring of negligible mass having a spring constant of 100 N/m (Fig. P5.76). The block is released from rest when the spring is unstretched, and the pulley is frictionless. The block moves 17.4 cm down the incline before coming to rest. Find the coefficient of kinetic friction between the block and incline.