NEET Physics: moment of a force Practice Questions
15 free multiple-choice questions on moment of a force (Rotational Motion) for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. If a force F is applied perpendicularly to a radius r, the magnitude of the resulting moment of force is given by:
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Correct answer: A — rF
When the force is applied perpendicularly (θ= 90°), the moment of force is calculated as the product of the magnitude of the force and the perpendicular distance (radius), τ= rF.
Q2. If a force is applied to a lever at a distance r from the pivot, and the force is applied perpendicular to the lever, what is the magnitude of the moment of this force?
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Correct answer: A — F · r
The moment of a force is calculated as the product of the perpendicular distance (lever arm, r) and the force (F).
Q3. The magnitude of the moment of a force acting on an object depends directly on which two factors?
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Correct answer: D — Force and perpendicular distance
The moment of a force is the product of the magnitude of the force and the perpendicular distance from the axis of rotation to the line of action of the force.
Q4. What is the unit of the moment of a force in the SI system?
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Correct answer: D — Joule
The moment of a force (torque) is calculated as Force × Perpendicular Distance. The SI unit for torque is Newton-meter (N·m), which is equivalent to Joule (J) since 1 J = 1 N·m.
Q5. For a given force acting at a fixed distance from the pivot, if the angle between the force vector and the lever arm is decreased, what happens to the moment produced?
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Correct answer: D — It decreases
The moment of force is proportional to the sine of the angle between the force and the lever arm (τ= rFsin θ). Decreasing the angle decreases sin θ, thus decreasing the moment.
Q6. When the moment of a force acting on a body is zero, what does this imply about the rotation of the body?
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Correct answer: A — The body is neither rotating nor accelerating rotationally.
A zero moment of force means there is no tendency to cause rotation, implying that the object is either not rotating or rotating with a constant angular velocity (no angular acceleration).
Q7. The relationship between torque (τ), moment of inertia (I), and angular acceleration (α) is defined by the equation:
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Correct answer: A — τ= Iα
This equation is the rotational equivalent of Newton's second law (F=ma), where torque is the rotational force, moment of inertia is rotational mass, and angular acceleration is rotational acceleration.
Q8. The rotational equivalent of linear force is known as:
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Correct answer: A — Torque
Torque is the rotational equivalent of force. It measures the twisting effect that causes an object to rotate.
Q9. Two forces acting on a rigid body are equal in magnitude and are applied along the same line. What is the resultant moment of these two forces about a point?
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Correct answer: D — Zero
Since the forces act along the same line (or the same line of action, assuming the distance to the pivot is the same), they produce moments in the same direction, but if they act along the same line through the pivot, they do not contribute to the rotation about that pivot point. If the forces are collinear, the net torque is zero if calculated about the point where they meet.
Q10. The rotational equivalent of force is known as:
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Correct answer: A — Torque
Torque (τ) is the rotational equivalent of force. It measures the effect of a force on the rotational motion.
Q11. A force is applied such that it acts along the radius vector of rotation. In this case, the moment of the force produced about the axis of rotation is:
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Correct answer: C — Zero
The moment of a force is calculated as τ= rF sin θ. If the force acts along the radius (i.e., θ= 90°), the perpendicular component is maximized. If the force acts along the radius, the perpendicular component (lever arm) is zero.
Q12. If a force is applied perpendicularly to the line connecting the point of application and the axis of rotation, what is the resulting moment of the force?
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Correct answer: A — Maximum
When the force is applied perpendicularly, the lever arm is maximized, resulting in the maximum possible moment of the force for a given force and distance.
Q13. If the distance between the point where the force is applied and the axis of rotation is doubled, and the force remains constant, how does the moment of the force change?
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Correct answer: B — It is doubled
Since the moment is directly proportional to the distance (lever arm), doubling the distance will double the resulting moment of the force.
Q14. When a force acts on a body, if the line of action of the force is parallel to the position vector from the pivot point to the point of application, what is the resulting moment of the force?
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Correct answer: A — Zero moment
Since the moment depends on the perpendicular distance, if the force is parallel to the position vector, the perpendicular distance is zero, resulting in a zero moment.
Q15. The formula for calculating the moment of a force is given by the product of the force and the perpendicular distance from the axis of rotation. This perpendicular distance is known as:
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Correct answer: D — Perpendicular distance
The perpendicular distance from the axis of rotation to the line of action of the force is crucial for determining the torque.
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