Question

A body falling freely under gravity passes two points 30 m apart in 1s. From what point above the upper point it began to fall?(Take g = 9.8 m $s^2$).

• A. 32.1 m
• B. 16.0 m
• C. 8.6 m
• D. 4.0 m

Answer 1

The correct option is A 32.1 m

$AC=0+\frac{1}{2}g(t_1+1{)}^2$ and $AB=\frac{1}{2}g{t}_1^2$

$AC-AB=30m$

$⟹\frac{1}{2}g\left[\right(t_1+1{)}^2-t_1^2]=30$

$⟹2t_1+1=\frac{60}{g}$

$⟹t_1=2.56[g=9.8]$

$AB=\frac{1}{2}g(t_1{)}^2=32.1m$