Question

A particle falling with constant acceleration covers $3m$ distance in third second of its motion. The distance covered in first $5$ second shall be: (Take $g=10m{s}^{-2}$)

• A. $5m$
• B. $15m$
• C. $30m$
• D. $45m$

Answer 1

The correct option is B $15m$

$s_n=u+\frac{a}{2}(2n-1)$

$\Rightarrow 3=u+\frac{10}{2}(2\times 3-1)\Rightarrow u=-22m/s$

$\therefore s=-22\times 5+\frac{1}{2}\times 10(5{)}^2=15m$