Question

Assertion: Two bodies of masses `M` and `m(M gt m)` are allowed to fall from the same height if the air resistance for each be the same then both the bodies will reach the earth simultaneously.
Reason: For same air resistance, acceleration of both the bodies will be same.
A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer 1

Correct Answer - D
The force acting on the body of mass `M` are its weight `Mg` acting vertically downwards and air resistance `F` acting vertically upward.
Acceleration of the bodies
`a_M = (Mg - F)/(M) = g - (F)/(M)`
Similarly `a_m = g - (F)/(m)`
Now, `M gt m`, therefore, the body with larger mass will have greater acceleration and it will reach the ground first.