Question

A force of 100 N is required to just set in motion a concrete block weighing 150 N on a flat surface. What is the coefficient of limiting static friction between the concrete and the surface material?

Answer 1

By force balance on concrete block,

Fnet = m*a

here, Fnet = net force on concrete block = F - fr

F = applied force = 100 N

fr = friction force on block = *N

N = normal force = weight of block = 100 N

a = acceleration of block = 0 (As, block just starts to motion.)

So, F - fr = 0

fr = F

*N = F

= 100/150 = 2/3

= 0.667

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