Work, Energy and Power
No work is done by a force on an object if
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 ?
a) force applied by the boy is in the same direction that of displacement so work done is positive
b) when ball is moving upward gravitational force is in opposite direction of displacement so work done is negative.
But when ball falls back gravitational force is in the same direction as that of displacement so work done by gravity is positive
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?
It is possible that a force is acting on a body but still the work done is zero? Explain given the example.
What are the quantities on which the amount of work done depends ? How are they related to work ?
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