Question

Assertion (A): The work done by gravity on an ascending body is negative.
Reason (R): The displacement and gravitational force are opposite in direction.

• A. A and R are true and R is the correct explanation of A.
• B. A and R are true, but R is not the correct explanation of A.
• C. A is true but R is false.
• D. Both A and R are false.

Answer 1

The correct option is A

A and R are true and R is the correct explanation of A.

Step 1: Explanation for the Assertion statement

1. Work done by gravity is given by the equation,
   $W=mgh$ Where W is the work done, m is the mass of the object, g is the value of acceleration due to gravity and h is the height of the object from the ground.
2. If an object moves against the direction of gravity then such motions are said to be ascending motion.
3. An object which is raised through a height h by applying some force is an example of ascending motion.
4. The work done by the gravitational force on this ascending object is
   $W=m(-g)h=-mgh$
5. So, The work done by the gravitational force on this ascending object is always negative.

Step 2: Explanation for the reason statement

1. When the object is ascending the direction of the object is upwards.
2. So, the displacement of the object will be upwards
3. The direction of Gravitational force acting on that object will be in a downward direction(towards earth).
4. So, The displacement and gravitational force are opposite in direction.
5. The reason given is true and it is the correct explanation for assertion.

Hence,

option (a) is correct.