After struggling to move the refrigerator in Problem 41, you finally apply enoug

Question

After struggling to move the refrigerator in Problem 41, you finally apply enough force to get it moving. What is the minimum force required to keep it moving with a constant velocity? Assume _K= 0.20. You are trying to slide a refrigerator across a horizontal floor. The mass of the refrigerator is 200 kg, and you need to exert a force of 350 N to make it just begin to move. (a) What is the coefficient of static friction between the floor and the refrigerator? (b) After it starts moving, the refrigerator reaches a speed of 2.0 m/s after 5.0 s. What is the coefficient of kinetic friction between the refrigerator and the floor?

Explanation / Answer

Given,

m = 200 kg ; F = 350 N

(a)For the mass to move

F = u mg

u = F/mg = 350/200 x 9.8 = 0.18

Hence, u = 0.18

b)from ewqn of motion

v = u + at

a = v/t = 2/5 = 0.4 m/s^2

The net force is:

Fnet = ma = F - u mg

200 x 0.4 = 350 - uk x 200 x 9.8 =>uk = 0.14

Hence, uk = 0.14

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