First slide

Gravitaional potential energy

Question

What is the weight of a body at a distance 2r from the centre of the earth if the gravitational potential energy of the body at a distance r from the centre of the earth is U

Easy

A

$U / 2 r$
B

$U / 3 r$
C

$U / 4 r$
D

Ur

Solution

$\begin{array}{l} W = m g = m (\frac{G M}{R^{2}}) \\ \begin{aligned} U & = \frac{G M m}{r} or G M = (U r / m) \\ ∴ W & = m (\frac{U r}{m}) \times \frac{1}{R^{2}} = m (\frac{U r}{m}) \times \frac{1}{(2 r)^{2}} \\ = \frac{U}{4 r} \end{aligned} \end{array}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App