SATHEE: Centre of Mass 3 Question 1

Centre of Mass 3 Question 1

1. A man (mass $= 50 k g$ ) and his son (mass $= 20 k g$ ) are standing on a frictionless surface facing each other. The man pushes his son, so that he starts moving at a speed of $0.70 m s^{- 1}$ with respect to the man. The speed of the man with respect to the surface is

(2019 Main, 12 April I)

(a) $0.28 m s^{- 1}$

(b) $0.20 m s^{- 1}$

(d) $0.14 m s^{- 1}$

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Answer:

Correct Answer: 1. (b)

Solution:

The given situation can be shown as below

Using momentum conservation law,

$= (Total momentum)_{after collision}$

$\begin{matrix} (m_{1} \times 0) + (m_{2} \times 0) = m_{1} v_{1} + m_{2} v_{2} \\ 0 = m_{1} (- v_{1}) \hat{i} + m_{2} v_{2} \hat{i} \end{matrix}$

$\begin{aligned} \Rightarrow & m_{1} v_{1} & = m_{2} v_{2} \\ \Rightarrow & 50 v_{1} & = 20 v_{2} \\ \Rightarrow & v_{2} & = 2.5 v_{1} \end{aligned}$

Again, relative velocity $= 0.70 m / s$

But from figure, relative velocity $= v_{1} + v_{2}$

$∴ v_{1} + v_{2} = 0.7$

From Eqs. (i) and (ii), we get

$v_{1} + 2.5 v_{1} = 0.7$

$\Rightarrow v_{1} (3.5) = 0.7$

$v_{1} = \frac{0.7}{3.5} = 0.20 m / s$

Centre of Mass 3 Question 1

1. A man (mass $= 50 k g$ ) and his son (mass $= 20 k g$ ) are standing on a frictionless surface facing each other. The man pushes his son, so that he starts moving at a speed of $0.70 m s^{- 1}$ with respect to the man. The speed of the man with respect to the surface is

Answer:

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Centre of Mass 3 Question 1

1. A man (mass =50kg ) and his son (mass =20kg ) are standing on a frictionless surface facing each other. The man pushes his son, so that he starts moving at a speed of 0.70ms−1 with respect to the man. The speed of the man with respect to the surface is

Answer:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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1. A man (mass $= 50 k g$ ) and his son (mass $= 20 k g$ ) are standing on a frictionless surface facing each other. The man pushes his son, so that he starts moving at a speed of $0.70 m s^{- 1}$ with respect to the man. The speed of the man with respect to the surface is