Question

A ball is thrown horizontally with initial velocity $40m/s$ from a building. It hits the ground after $3$ seconds. Calculate the total speed when it hits the ground. (Ignore air resistance.)

• A. $30m/s$
• B. $40m/s$
• C. $50m/s$
• D. $60m/s$
• E. $70m/s$

Answer 1

The correct option is C $50m/s$

Given : $u_x=u=40m/s$ $T=3$ s

x direction : $a_x=0$ $⟹V_x=u_x=40$ $m/s$

y direction : $u_y=0$ $a_y=g=10m/s^2$

Using $V_y=u_y+a_{y}T$

$\therefore$ $V_y=0+10\times 3=30$ $m/s$

$\therefore$ Speed of the ball $V=\sqrt{V_x^2+V_y^2}=\sqrt{(40{)}^2+(30{)}^2}=50$ $m/s$