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# An object weighs 100N on the earth's surface. Find its weight at a point P with o...

### Question

An object weighs 100N on the earth's surface. Find its weight at a point P with orbital radius 2R. [g =10Nkg$$^{-1}$$]

A) 40.0N

B) 35.0N

C) 25.0N

D) 20.0N

### Explanation:

Weight, W = mg, W = 100N, g = 10Nkg$$^{-1}$$
$$m = \cfrac{W}{g} = \cfrac{100}{10} = 10$$kg
$$g = \cfrac{GM}{R^2};$$
$$g_1R_1^2 = g_2R_2^2$$
$$R_2 = 2R; g = \cfrac{10R^2}{4R^2} = 2.5$$Nkg$$^{-1}$$
Weight of object at 2;
$$W = mg = 10 \times 2.5 = 25N$$

## Dicussion (1)

• Weight, W = mg, W = 100N, g = 10Nkg$$^{-1}$$
$$m = \cfrac{W}{g} = \cfrac{100}{10} = 10$$kg
$$g = \cfrac{GM}{R^2};$$
$$g_1R_1^2 = g_2R_2^2$$
$$R_2 = 2R; g = \cfrac{10R^2}{4R^2} = 2.5$$Nkg$$^{-1}$$
Weight of object at 2;
$$W = mg = 10 \times 2.5 = 25N$$