During motion of a planet from perihelion to aphelion work done by gravitational force of sun on it

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7.Gravitation

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During motion of a planet from perihelion to aphelion the work done by gravitational force of sun on it is ...........

A

Zero

B

Negative

C

Positive

D

May be positive or negative

Solution

(b)

According to Kepler's Law of areas, $v_A < v_P$

$v_A=$ speed of planet at aphelion

$v_P=$ speed of planet at perihelion

Now, work done by gravitational force of sun $=\Delta K \cdot E=\frac{1}{2} m\left(v_A^2-v_P^2\right)$

$\Rightarrow W_{\text {gravitation force }}$ is negative.

Standard 11

Physics

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