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  • A body is falling freely under the action of gravity alone in vacuum. Which of the following quantities remain constant during the fall? a) kinetic energy

A body is falling freely under the action of gravity alone in vacuum. Which of the following quantities remain constant during the fall?

a) kinetic energy

b) potential energy

c) total mechanical energy

d) total linear momentum

Answers (1)

The answer is the option (c) total linear momentum

Under the effect of the conservative forces, for a free-falling body, the potential energy decreases and the kinetic energy increases continuously. This leads to the total energy (KE +PE) remaining constant.

E = \frac{1}{2} mv^{2} + mgh

Velocity is zero at point A, so KE is also zero and Ea = mgH

At point B, Vb =\sqrt{ 2gh} 

Eb = \frac{1}{2} m(2gh) + mg(H-h)

Eb = mgH

At point C,Vc = \sqrt{2gh}

Ec = \frac{1}{2} m(2gH) + mg (0)

Ec = mgH

Hence the total mechanical energy remains the same.

Posted by

infoexpert24

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