question_answer

Ten one- rupee coins are put on top of each other on a table. Each coin has a mass m. Which of the following statements is not true?

A)  The force on the 6th coin (counted from the bottom) due to all the coins on its top is equal to 4mg (downwards)

B)  The force on 6th coin due to 7th coin is 4mg (downwards)

C)  The reaction of the 6th coin on the 7th coin is 4mg (upwards)                    

D)  The total force on the 10th coin in 9 mg (downwards)

Correct Answer: D

Solution :

                 Ten coins are placed one over another as shown. As the 6th coin has 4 coins on its top, therefore the force experienced by the 6th coin will be 4 mg. As 7th coin has 3 coin on its top, therefore it will exert a force of 4 mg on 6th coin. As every action has equal and opposite   reaction therefore 6th coin will give reaction of 4 mg to the coin              upwards                 The 10th coin will experience a reaction force of 1 mg as it exerts a force of 1 mg.