STANDARDPhysics-Laws of Motion
STANDARD Physics Friction MCQ Question
Type: MCQ-conceptual-Medium-Class 11
A block of mass 2 kg rest on a plane inclined at an angle of 30° with the horizontal. The coefficient of friction between the block and the surface is 0.7. What will be the frictional force acting on the block? (take g = 9.8 m/s²)
A
10.3 N
B
23.8 N
C
9.8 N
D
6.3 N
Correct Answer
Option C
Detailed Explanation
As the block is at rest, the maximum force of static friction fₛ = μₛR. But R = mg cos θ, so fₛ = μₛ mg cos θ = 0.7 × 2 × 9.8 cos 30° = 11.9 N. However, the actual force of static friction cannot exceed the force due to gravity (mg sin θ) acting down the plane. The actual force of static friction = mg sin θ = 9.8 N.
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