Question

Two balls A and B of same size are dropped from the same point under gravity. The mass of A is greater than that of B. If the air resistance acting on each ball is same, then:

• A. both the balls reach the ground simultaneously
• B. the ball A reaches earlier
• C. the ball B reaches earlier
• D. nothing can be said

Answer 1

The correct option is B the ball A reaches earlier

Since the air resistance is same thus they have same forces acting on them (air resistance and gravity). The force equation for masses A and B will be
$M_{A}g-R=M_A\times a_A$...(i)
$M_{B}g-R=M_B\times a_B$...(ii)
where $R$ is air resistance force and,$g$ is acceleration due to gravity.
$a_A=g-\frac{R}{M_A}{a}_B=g-\frac{R}{M_B}$
$M_A>M_B\Rightarrow a_A>a_B$