Sir there was a question in the work and energy's 1st class test..
And tht question was as follows:
Which of the following statements about work done by a force is incorrect?:
A) Work is done by a force only if the body moves towards the direction of the applied force.
B) Work done by a body is equal to the amount of energy gained or spent by the body.
C) Work done by a force can be 0 even if the object moves to a certain distance.
D) Work done by a force can be positive as well as negative.
Sir in this question the correct was (A) according to the test..
But it should be C ryt? coz work done by a force cannot be 0 even if the object moves to a certain distance!!
So C is the incorrect option..
But i didn't understand that how Option A is the correct ans..
Pls explain!!
Dear Student,
The answer is option A.
Work is done by a force if the body moves in the direction or opposite that of the applied force. If applied force and displacement are in the same direction,we call it as positive work.Example: Pushing a box in the horizontal surface.Here,force and displacement are in same direction.So work done is positive.
If applied force and displacement are in the opposite direction,we call it as negative work.
Example:When we throw a ball upwards, the gravitational force on the ball acts downwards.But the displacement of the body is upwards.So work done by gravitational force is negative here.
Option C is true. Work done by a force can be zero even if the object moves a certain distance.It is called zero work.It occurs when the direction of applied force and displacement are perpendicular to each other.
Example:When we hold an object and walk,the gravitational force acts in downward direction whereas displacement acts in forward direction.(In the direction of our motion)Hence work done by gravitational force is zero.
Regards.
The answer is option A.
Work is done by a force if the body moves in the direction or opposite that of the applied force. If applied force and displacement are in the same direction,we call it as positive work.Example: Pushing a box in the horizontal surface.Here,force and displacement are in same direction.So work done is positive.
If applied force and displacement are in the opposite direction,we call it as negative work.
Example:When we throw a ball upwards, the gravitational force on the ball acts downwards.But the displacement of the body is upwards.So work done by gravitational force is negative here.
Option C is true. Work done by a force can be zero even if the object moves a certain distance.It is called zero work.It occurs when the direction of applied force and displacement are perpendicular to each other.
Example:When we hold an object and walk,the gravitational force acts in downward direction whereas displacement acts in forward direction.(In the direction of our motion)Hence work done by gravitational force is zero.
Regards.