physics : class11 Line of Action : Moment of a Force : Motion of System of Particles and Rigid Body MCQ Questions and Answers
Practice important
Line of Action
MCQ questions and answers.
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MCQ Questions
1. What is meant by the line of action of a force?
A.
The path followed by the body
B.
The straight line passing through the point of application in the direction of the force
C.
The line perpendicular to the force
D.
The circular path of a rotating body
Correct Answer:
The straight line passing through the point of application in the direction of the force
Explanation:
The line of action is the straight line along which a force acts, passing through its point of application and having the force's direction.
2. The moment of a force about a point is zero when the line of action of the force:
A.
Is far from the point
B.
Is parallel to the ground
C.
Passes through the point
D.
Is perpendicular to the ground
Correct Answer:
Passes through the point
Explanation:
When the line of action passes through the reference point, the perpendicular distance from the point to the line of action is zero, so the moment is zero.
3. The perpendicular distance from a point to the line of action of a force is called the:
A.
Radius of the force
B.
Lever arm
C.
Displacement of the body
D.
Length of the force
Correct Answer:
Lever arm
Explanation:
The lever arm is the shortest perpendicular distance between the reference point and the line of action of the force.
4. For a given force and reference point, the moment of the force becomes larger when its line of action is:
A.
Closer to the reference point
B.
Farther from the reference point
C.
Made to pass through the reference point
D.
Removed from the body
Correct Answer:
Farther from the reference point
Explanation:
The moment equals the force multiplied by the perpendicular distance to its line of action. Increasing this distance increases the moment.
5. If a force is shifted along its own line of action, its moment about a fixed point remains:
A.
Unchanged
B.
Doubled
C.
Reduced to zero in every case
D.
Reversed in direction
Correct Answer:
Unchanged
Explanation:
Shifting a force along the same line of action does not change the perpendicular distance from the fixed point to that line, so the moment remains unchanged.
6. Which distance is used to calculate the moment of a force about a point?
A.
The distance along the force
B.
The total distance travelled by the body
C.
The perpendicular distance from the point to the line of action
D.
The distance between two endpoints of the body
Correct Answer:
The perpendicular distance from the point to the line of action
Explanation:
Moment is calculated using the perpendicular distance between the reference point and the force's line of action.
7. A force acts along a line that does not pass through a pivot. The moment of the force about the pivot is generally:
A.
Zero
B.
Non-zero
C.
Always equal to the force
D.
Always equal to the pivot distance
Correct Answer:
Non-zero
Explanation:
If the line of action does not pass through the pivot, there is a non-zero perpendicular distance and therefore generally a non-zero moment.
8. If two forces have equal magnitudes and the same line of action, their moments about a point depend on their:
A.
Colours
B.
Perpendicular distances from the point to the line of action
C.
Names
D.
Masses only
Correct Answer:
Perpendicular distances from the point to the line of action
Explanation:
For equal forces, the moment is determined by the perpendicular distance from the reference point to each force's line of action.
9. A force has a line of action passing through point O. What is its moment about point O?
A.
Zero
B.
Equal to the force magnitude
C.
Maximum
D.
Equal to the distance travelled
Correct Answer:
Zero
Explanation:
The perpendicular distance from O to the line of action is zero because the line passes through O, so the moment about O is zero.
10. Changing the point of application of a force without changing its line of action will change the moment about a point by:
A.
Making it necessarily zero
B.
Making it necessarily double
C.
Making no change
D.
Reversing its direction necessarily
Correct Answer:
Making no change
Explanation:
The moment about a point depends on the force and the perpendicular distance to its line of action. If the line of action is unchanged, the moment is unchanged.
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Line of Action
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