Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • Engineering
  • A boy of mass 20kg is standing on a 80kg free to move long cart. There is negligible friction between cart and ground.  Initially, the boy is standing 25 m from a wall. If he walks 1

A boy of mass 20kg is standing on a 80kg free to move long cart. There is negligible friction between cart and ground.  Initially, the boy is standing 25 m from a wall. If he walks 10m on the cart towards the wall, then the final distance of the boy from the wall will be:

Option: 1

15m


Option: 2

12.5m


Option: 3

15.5m


Option: 4

17 m


Answers (1)

best_answer

As there is no external force, so the displacement of the centre of mass of the cart + boy system parallel to the surface is zero

\begin{aligned} &\Delta \mathbf{x}_{\mathrm{cm}}=\frac{\mathbf{m}_{1} \Delta \mathbf{x}_{1}+\mathbf{m}_{1} \Delta \mathbf{x}_{1}}{\mathbf{m}_{1}+\mathbf{m}_{2}}\\ &0=\frac{\mathbf{m}_{1} \Delta \mathbf{x}_{1}+\mathbf{m}_{1} \Delta \mathbf{x}_{1}}{\mathbf{m}_{1}+\mathbf{m}_{2}} \end{aligned}

Let the boy moves towards the wall a distance of 10 m and the cart moves away from the wall a distance of x 

so, displacement of man wrt ground towards the wall is  \Delta x_{1}=10-x

displacement of cart wrt ground towards the wall  is \Delta x_{2}=-x

\begin{aligned} &\mathrm{m}_{1} \Delta \mathrm{x}_{1}+\mathrm{m}_{2} \Delta \mathrm{x}_{2}=0\\ &20(10-\mathrm{x})+80(-\mathrm{x})=0\\ &100 x=200\\ &\mathbf{x}=2 \mathrm{m} \end{aligned}

displacement of man wrt ground towards the wall is \Delta x_{1}=10-2=8

So his distance from the wall = X=25-8=17

Posted by

Rishabh

View full answer

JEE Main high-scoring chapters and topics

Study 40% syllabus and score up to 100% marks in JEE

Similar Questions

Trending Articles/News

anam-khan

BSEB Super 50 coaching application reopens tomorrow for JEE, NEET aspirants
anam-khan

Telangana to offer free JEE, NEET, CLAT coaching to government school students
anam-khan

BTech 2025 Admission LIVE: JoSAA revised schedule out on josaa.nic.in; updates on MHT CET, KEAM counselling

Latest Question