Ten one-rupee coins are put 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 7th coin (counted from the bottom) due to all the coins on its top,
B. the force on the 7th coin by the eighth coin,
C. the reaction of the 6th coin on the 7th coin.
Given:
Mass of each coin = m Kg
Number of coins = 10
(a) Force on the 7the coin from bottom is exerted by the weight of the 3 coins above it.
F = 3× (m× g)
F = 3mg
The force is vertically downward.
(b) Force on the seventh coin due to the eighth coin is the sum of force by all the coins above it.
Since there are 2 more coins above coin 8, so the force on coin 7 due to 8 is given by,
F = mg + 2mg
F = 3mg
The force acts vertically downwards.
(c) The 6th coin has 4 coins above it hence it experiences the force,
F = 4 × mg
From Newton’s 3rd law of motion we conclude that coin 6, exerts an equal force in upward direction.
R = 4× mg
This reaction is in upward direction.