Question

A ball is thrown vertically upward
and it reaches a height of 90m.
Find the velocity with which it was
thrown​​

Answer 1

Given Parameters :

• Displacement (s) = 90 m
• Final Velocity (v) = 0 m/s
• Acceleration due to gravity = -9.8 m/s² (Ball thrown upwards)

Unknown :

◉ The velocity with which it was thrown

• Initial Velocity (u) = ?

Answer:

Using third equation of motion :-

• v² = u² + 2as

Plug in the given values :

$=> \sf v^2 = u^2 + 2as$

$=> \sf v^2 - u^2 = 2as$

$=> \sf (0)^2 - u^2 = 2( - 9.8)(90)$

$=> \sf - u^2 = 2( - 9.8)(90)$

$=> \sf - u^2 = - 1764$

$=> \sf u^2 = 1764$

$=> \sf u = \sqrt{1764 }$

$=> \sf u = \sqrt{2 \times 2 \times 3 \times 3 \times 7 \times 7}$

$=> \sf u = 2 \times 3 \times 7$

$=> \underline{ \boxed{\sf u = 42 \: m/s}}$

Therefore, The velocity at which the ball was thrown was 42 m/s.