A block of mass m is held in equilibrium against a vertical wall by a horizontal force. If the coefficient of friction between the wall and the block is µ, the minimum value of the horizontal force is
Attached Figure / Diagram
A
µmg
B
(1-µ)mg
C
(1+µ)mg
D
mg/µ
Verified Correct Answer: D.
Physical Principles & Numerical Solution
To keep the block of mass m in equilibrium against a vertical wall using a horizontal force F:
The normal reaction N = F
The frictional force f must balance the weight: f = mg
Maximum friction available: f = \muN = \muF
For the minimum horizontal force:
\muF = mg
F = mg / \mu
Source: Myschool Past Questions Archive (Record #41683)