Question

An object of mass 5 kg is thrown vertically upwards from the ground. The air resistance produces a constant retarding force of 10 N throughout the motion. The ratio of time of ascent to the time of descent will be equal to [Use $g$ = $10 \;ms^{–2}$].

• A. 1 : 1
• B. $\sqrt2 : \sqrt3$
• C. $\sqrt3 : \sqrt2$
• D. 2 : 3

Answer 1

Answer: (B)

$\sqrt2 : \sqrt3$

Answer 2

Let time taken to ascent is $t_1$ and that to descent is $t_2$. Height will be same so

$H = \frac{1}{2} \times 12t^2_1=\frac{1}{2} \times 8t^2_2$

⇒ $\frac{t_1}{t_2} = \frac{\sqrt{2}}{\sqrt{3}}$