Work, Energy and Power
No work is done by a force on an object if
It is possible that a force is acting on a body but still the work done is zero? Explain given the example.
Yes, if force is acting on a body work done can be zero. When an object is at rest and no external force except gravity is acting on it in this case the work that would be zero as the force acting on it is perpendicular.
For example,
When an object is at rest and no external force except gravity is acting on it in this case the work that would be zero as the force acting on it is perpendicular. Therefore the displacement is zero and if displacement is zero work done would be zero.
We know that,
The work done
$$W=fs$$
Suppose that displacement is zero then,
$$ W=f\times 0 $$
$$ W=0 $$
The work done is zero.
No work is done by a force on an object if
When a body moves with constant speed in a circular path, then:
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.
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?
When does a force perform work?
What are the quantities on which the amount of work done depends ? How are they related to work ?
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 ?
How much work is done when a body of mass $$m$$ is raised to a height is above the ground?
Give one example each in which force does (a) positive work (b) negative work (c) zero work
When is the work done by a force on a body: a) positive b) negative c) zero