Ten one-rupee coins are placed on top of each other on a table. Each coin has a mass $m$. Give the magnitude and direction of:
$(a)$ The force on the $7^{\text{th}}$ coin (counted from the bottom) due to all the coins on its top.
$(b)$ The force on the $7^{\text{th}}$ coin by the $8^{\text{th}}$ coin.
$(c)$ The reaction of the $6^{\text{th}}$ coin on the $7^{\text{th}}$ coin.

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(N/A) The force on the $7^{\text{th}}$ coin is exerted by the weight of the three coins $(8^{\text{th}}, 9^{\text{th}}, 10^{\text{th}})$ on its top.
Weight of one coin $= mg$.
Weight of three coins $= 3mg$.
Hence,the force exerted on the $7^{\text{th}}$ coin by the three coins on its top is $3mg$. This force acts vertically downward.
$(b)$ The force on the $7^{\text{th}}$ coin by the $8^{\text{th}}$ coin is equal to the weight of all the coins above the $7^{\text{th}}$ coin,which are the $8^{\text{th}}, 9^{\text{th}},$ and $10^{\text{th}}$ coins.
Total weight $= mg + mg + mg = 3mg$.
Hence,the force exerted by the $8^{\text{th}}$ coin on the $7^{\text{th}}$ coin is $3mg$ acting vertically downward.
$(c)$ The $6^{\text{th}}$ coin supports the weight of all coins above it,which are the $7^{\text{th}}, 8^{\text{th}}, 9^{\text{th}},$ and $10^{\text{th}}$ coins.
Total weight supported by the $6^{\text{th}}$ coin $= 4mg$.
According to Newton's third law of motion,the $6^{\text{th}}$ coin exerts an equal and opposite reaction force on the $7^{\text{th}}$ coin.
Therefore,the reaction force of the $6^{\text{th}}$ coin on the $7^{\text{th}}$ coin is $4mg$ acting vertically upward.

Explore More

Similar Questions

$A$ $1 \text{ N}$ pendulum bob is held at an angle $\theta$ from the vertical by a $2 \text{ N}$ horizontal force $F$ as shown in the figure. The tension in the string supporting the pendulum bob (in newton) is

The adjacent figure shows a part of a horizontally stretched net. Section $AB$ is stretched with a force of $10 \,N$. The tensions in the sections $BC$ and $BF$ are

$A$ body is in equilibrium under the action of three coplanar forces $P, Q$ and $R$ as shown in the figure. Select the correct statement.

What is the minimum number of forces acting in the same plane on a particle that can result in a zero net force?

At the instant $t = 0$,a force $F = kt$ ($k$ is a constant) acts on a small body of mass $m$ resting on a smooth horizontal surface. The force is applied at an angle $\alpha$ with the horizontal. The time at which the body leaves the surface is:

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo