Question -
Answer -
(a) Force on the seventh coin is exerted by theweight of the three coins on its top.
Weight of one coin = mg
Weight of three coins = 3mg
Hence, the force exerted on the 7th coinby the three coins on its top is 3mg. This force acts verticallydownward.
(b) Force on the seventh coin by the eighth coinis because of the weight of the eighth coin and the other two coins (ninth andtenth) on its top.
Weight of the eighth coin = mg
Weight of the ninth coin = mg
Weight of the tenth coin = mg
Total weight of these three coins = 3mg
Hence, the force exerted on the 7th coinby the eighth coin is 3mg. This force acts vertically downward.
(c) The 6th coin experiences adownward force because of the weight of the four coins (7th, 8th,9th, and 10th) on its top.
Therefore, the total downward forceexperienced by the 6th coin is 4mg.
Asper Newton’s third law of motion, the 6th coin will produce anequal reaction force on the 7th coin, but in the oppositedirection. Hence, the reaction force of the 6th coin on the 7th coinis of magnitude 4mg. This force acts in the upward direction.