NEETPhysicsWork, Power and Energy
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): When a ball dropped from a height h loses 75 % of its kinetic energy on striking the ground, it will rebound to a height of h/4 . Reason (R): The rebound velocity of the ball is directly proportional to the square root of its remaining kinetic energy. In the light of the above statements, choose th
Options
- ABoth Assertion and Reason are true and Reason is the correct explanation of Assertion.
- BBoth Assertion and Reason are true but Reason is not the correct explanation of Assertion.
- CAssertion is true but Reason is false.
- DAssertion is false but Reason is true.
Correct answer
B. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
Step-by-step solution
Assertion is true: The kinetic energy just before striking the ground is E = mgh . If 75 % of the kinetic energy is lost, the remaining kinetic energy is 25 % of E , which is E/4 . The rebound height h' is given by mgh' = E/4 = mgh/4 , so h' = h/4 . Reason is true: Kinetic energy is K = 1 2 mv^2 , which means v = 2K m . Thus, the rebound velocity is directly proportional to the square root of the remaining kinetic energy. However, the Reason does not correctly explain the Assertion. The correct explanation for the