Torque

Practice Questions:

Question 1: difficult

An equilateral prism of mass m rests on a rough horizontal surface with coefficient of friction μ. A horizontal force F is applied on the prism as shown in the figure. If the coefficient of friction is sufficiently high so that the prism does not slide before toppling, then the minimum force required to topple the prism is :

1. mg/√3

2. mg/4

3. μmg/√3

4. 3mg/4

View Answer

Toppling will take place about right most point so,

F ×(√3a/2) = mg × a/2

⇒ F= mg/√3

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Question 2: difficult

A cubical block of mass m and edge a slides down a rough inclined plane of inclination θ with a uniform speed. Find the torque of the normal force acting on the block about its centre

1. m g a sin θ

2. (m g a sin θ)/3

3. (m g a sin θ)/4

4. (m g a sin θ)/2

View Answer

As the object slides with constant speed friction force is balancing mgsinθ. Torque of Normal reaction and friction force about centre of object will cancel each other.

τ=mg.sinθ × a/2 = (mg a sinθ)/2

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