Question

A block of mass 2 kg falls from the wall at a height of 2.3 m. Calculate the velocity just before it hits the ground. ($g=-9.8\frac{m}{s^2}$)

• A. $-6.76\frac{m}{s}$
• B. $-26.86\frac{m}{s^2}$
• C. $45.08\frac{m}{s}$
• D. $13.43\frac{m}{s}$
• E. $3.36\frac{m}{s}$

Answer 1

The correct option is A $-6.76\frac{m}{s}$

Given :

$u=0m{s}^{-1}$; initial velocity

$a=-9.8m{s}^{-2}$; acceleration due to gravity

$h=2.3m$; height of the wall

Speed with which its hits the ground.

Apply third equation of motion-

$v^2=u^2+2gh$

$\Rightarrow v^2=0+2gh$

$\Rightarrow v=\sqrt{2gh}$

$\Rightarrow v=\sqrt{2\times 9.8\times 2.3}$

$\Rightarrow v=6.76m{s}^{-1}$ m/s

As the downward direction is taken to be a negative direction, thus the hitting velocity is $-6.76m{s}^{-1}$ m/s.