Ten one-rupee coins are put on top of each other on a table. Each coin has mass m. Give the magnitude and direction of

(i) the force on the 7th coin (counted from the bottom) due to all the coins on its top,

(ii) the force on the 7th coin by the 8 coin,

(iii) the reaction of the 6th coin on the 7th coin.

Mass of each coin = m

Number of total coins = 10

(i) Force acting on 7th coin (counted from the bottom)

= Weight of the coins above it =

Weight of 3 coins

= 3 mg N (downward)

(ii) Force acting on 7th coin by the 8th coin = weight of the 8 coin + weight of two coins supported by 8 coin

= mg + 2 mg

= 3 mg N (downward)

(iii) Reaction of the 6th coin on the 7th coin

= — (force exerted on 6th coin)

= — (weight of 4 coins)

= — 4 mg N (vertically upward)