### Which will touch the ground first ?

If iron ball and a rubber ball was allowed to fall freely.. From a great height .. Which will touch the ground first? Why.## Answers

They will both touch the ground at the same time provided that their surface areas are equal(this provides equal air resistance). This is because the velocity of free-fall is independent of a body's mass. ie. from the second equation of motion under gravity, h=ut+(1/2)g(t)2 for free-fall initial speed u=0. hence time t=sqt.(2h/g) hence for equal heights (h), time of free-fall is equal which means they'll reach the ground at the same time!

Force i.e f=mg for iron ball is high because it has more mass than rubber ball and therefore attains greater velocity and will reach first than rubber.

It depends upon the air resistance if we neglect the air resistance then they will reach the ground at the same time else iron ball will reach the ground first.

Both will touch the ground at same instant since the acceleration of a body due to gravity does no depends on mass of body its equal for both hence they move with equal velocity.

According to question bolls have constant velocity called terminal velocity therefore acceleration will be zero and now we apply newton's second law due to air the direction of drag force upward and due gravity mg downward direction they balancing each other and after calculation (see book for formula of drag force) the square of terminal velocity is directly proportional to density of boll so which boll has high density has high velocity and fall first . Answer is iron boll.