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Module by: Sunil Kumar Singh. E-mail the author

Summary: Objective questions, contained in this module with hidden solutions, help improve understanding of the topics covered under the module "Torque about a point".

The questions have been selected to enhance understanding of the topics covered in the module titled " Torque ". All questions are multiple choice questions with one or more correct answers.

## Understanding level (Torque about a point)

### Exercise 1

A force, “F”, acts on a particle at a linear distance “r” from the origin of a coordinate system. If force acts in coordinate plane “yz”, then the toque on the particle is :

(a) makes an angle “θ” with “–z” axis (b) makes an angle “θ” with x axis (c) acts along x axis (d) acts along “-x” axis (a) makes an angle “θ” with “–z” axis (b) makes an angle “θ” with x axis (c) acts along x axis (d) acts along “-x” axis

### Exercise 2

The torque on a particle at a position on x-axis (other than origin) is zero. If the force applied is not zero, then force is acting :

(a) either in “y” or “z” direction (b) in x direction (c) in ± x direction (d) - z direction (a) either in “y” or “z” direction (b) in x direction (c) in ± x direction (d) - z direction

### Exercise 3

The bob of a pendulum of length "L" is raised to one side and released to oscillate about the mid point. The torque about the point of suspension, at an instant when the bob makes an angle “θ” with respect to vertical, is :

(a) m g L sin θ (b) m g L cos θ (c) m g L tan θ (d) m g L cot θ (a) m g L sin θ (b) m g L cos θ (c) m g L tan θ (d) m g L cot θ

### Exercise 4

A force F = (2i + 2j – 3k) Newton acts on a particle, placed at a point given by r = (i + jk) meters. If the particle is constrained to rotate about x-axis along a circular path, then the magnitude of torque about the axis is :

(a) 1 (b) 2 (c) 3 (d) 4 (a) 1 (b) 2 (c) 3 (d) 4

### Exercise 5

In the figure, three forces of 10 N each act on a triangular plate as shown in the figure. If “C” be the center of mass of the plate, then torque, in N-m, about it is :

(a) 0.61 (b) - 1.33 (c) - 0.91 (d) - 1.11 (a) 0.61 (b) - 1.33 (c) - 0.91 (d) - 1.11

## Exercise 6

A force, “F”, acts on a particle lying in “xz” plane at a linear distance “r” from the origin of a coordinate system. If the direction of force "F" is parallel to y-axis, then the toque on the particle :

(a) makes an angle “θ” with “–z” axis (b) makes an angle “θ” with x - axis (c) acts along x – axis (d) acts along “-x” axis (a) makes an angle “θ” with “–z” axis (b) makes an angle “θ” with x - axis (c) acts along x – axis (d) acts along “-x” axis


1. (c)   2. (c)    3. (a)    4. (a)    5.  (c)
6. (b)


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