A block is pressed against a vertical wall by a horizontal force of and remains at rest

PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

3\,\text{kg}

block is pressed against a vertical wall by a horizontal force of

80\,\text{N}

and remains at rest. The coefficients of friction are

\mu_s = 0.5

and

\mu_k = 0.3

; take

g = 10\,\text{m/s}^2

. The horizontal force is suddenly reduced to

40\,\text{N}

. The subsequent acceleration of the block is (a)

3.3\,\text{m/s}^2

downward (b)

6\,\text{m/s}^2

downward (c) The block remains at rest (d)

2\,\text{m/s}^2

downward