# A Man of Mass 50 Kg Starts Moving on the Earth and Acquires a Speed 1.8 M/S. with What Speed Does the Earth Recoil? Mass of Earth = 6 × 1024 Kg. - Physics

Sum

A man of mass 50 kg starts moving on the earth and acquires a speed 1.8 m/s. With what speed does the earth recoil? Mass of earth = 6 × 1024 kg.

#### Solution

By the law of conservation of linear momentum, we have:
$m_1 v_1 = m_2 v_2$
Here, m1 and v1 are the mass and velocity of the man respectively, and m2 and v2 are the mass and velocity of the Earth respectively.

$\Rightarrow 50 \times 1 . 8 = 6 \times {10}^{24} \times v_2$

$\therefore v_2 = \frac{50 \times 1 . 8}{6 \times {10}^{24}} = 15 \times {10}^{- 24} m/s$

$\Rightarrow v_2 = 1 . 5 \times {10}^{- 23} m/s$
Hence, the earth recoils with a speed of 1.5 × 10−23 m/s.

Concept: Momentum Conservation and Centre of Mass Motion
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#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 9 Centre of Mass, Linear Momentum, Collision
Q 17 | Page 160