Question

(a)Which is greater the attraction of the Earth on 1kg of iron or the attraction of 1kg iron on the Earth?Why?
(b)A boy throws a ball vertically upwards and catches it back in 10s.Calculate
(i)the velocity with which it was thrown up and
(ii)maximum height attained by the ball (take g=10m/s)
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Answer 1

a)both earth and iron exerts equal force on each other and f=Gm1m2/r^2