You are trying to slide a refrigerator across a horizontal floor. The mass of th
ID: 2286937 • Letter: Y
Question
You are trying to slide a refrigerator across a horizontal floor. The mass of the refrigerator is 186 kg, and you need to exert a force of 342 N to make it just begin to move.
(a) What is the coefficient of static friction between the floor and the refrigerator?
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(b) After it starts moving, the refrigerator reaches a speed of 1.8 m/s after 4.5 s. What is the coefficient of kinetic friction between the refrigerator and the floor?
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Explanation / Answer
(a) The mass of the refrigerator is 186 kg, so it has a weight of 186 x 9.81 N
This weight is equal to the normal reaction (N)
The force due to friction is 342 N = coefficient of friction x N
coefficient of friction = 342 / (186 x 9.81)=0.1874
(b) The fridge has been accelerated by a force to make it go from 0 m/s to 1.8 m/s.
a=1.8/4.5=0.4
F = ma=186*0.4=74.4 N
Force on fridge is 74.4 N after breakaway.
coeffcient of dynamic friction is 74.4 / (186 x 9.81)=0.041
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