Work, Energy and Power
When a body moves with constant speed in a circular path, then:
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Multiple Choice
No work is done by a force on an object if
AThe force is always perpendicular to its velocity
Correct Answer
BThe force is always perpendicular to its acceleration
CThe object's center of mass is stationary but the point of application of the force moves on the object
DThe object moves in such a way that the point of application of the force remains fixed
Correct Answer
Solution
$$W=\int { F.ds } $$
So, motion of both object and point of application of force on the object is necessary in order to keep $$ds$$ non zero.
Also angle between force and displacement( velocity ) should not be $$90^0$$ to keep dot product non zero.
SIMILAR QUESTIONS
Work, Energy and Power
The sign of work done by a force on a body is important to understand. State carefully if the following quantities are positive or negative: (a) work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket. (b) work done by gravitational force in the above case, (c) work done by friction on a body sliding down an inclined plane, (d) work done by an applied force on a body moving on a rough horizontal plane with uniform velocity. (e) work done by the resistive force of air on a vibrating pendulum in bringing it to rest.
Work, Energy and Power
An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?
Work, Energy and Power
When does a force perform work?
Work, Energy and Power
It is possible that a force is acting on a body but still the work done is zero? Explain given the example.
Work, Energy and Power
What are the quantities on which the amount of work done depends ? How are they related to work ?
Work, Energy and Power
A boy throws a rubber ball vertically upwards. What type of work, positive or negative, is done : a) by the force applied by the boy? b) by the gravitational force of earth ?
Work, Energy and Power
How much work is done when a body of mass $$m$$ is raised to a height is above the ground?
Work, Energy and Power
Give one example each in which force does (a) positive work (b) negative work (c) zero work
Work, Energy and Power
When is the work done by a force on a body: a) positive b) negative c) zero
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