Question

From a point at some height one body is dropped, while a second body is thrown downward with an initial velocity of $1{\text{ms}}^{-1}$ simultaneously in the same vertical line. The separation between these is $1.8\text{m}$ after a time

• A. $4.5\text{s}$
• B. $9\text{s}$
• C. $1.8\text{s}$
• D. $36\text{s}$

Answer 1

The correct option is C $1.8\text{s}$

Using $s=ut+\frac{1}{2}a{t}^2$
And taking downward direction as positive,
For the dropped body, $h_1=\frac{1}{2}g{t}^2$;
For the thrown body, $h_2=1\times t+\frac{1}{2}g{t}^2=t+\frac{1}{2}g{t}^2$;
$h_2-h_1=t;$ So, $t=1.8\text{second}$
$\therefore$ (c)