Question

a ball is thrown vertically upwards and it reaches a height of 90m.find the velocity with which it was thrown

Answer 1

Answer:

the equation of motion v²-u² = 2as

At the peak of the ball’s flight, v=0

so u² = -2as

u² = -2 x -9.8 x 90=1764

u = √ 1764 = 42 m/s

Explanation:

hope it is useful.

Answer 2

Answer:

A ball is thrown vertically upwards and it reaches a height of 90m. The velocity with which it was thrown is $42.4264 \ m/s$

Explanation:

let v be the final velocity of the object, u be the initial velocity of the object, a be the acceleration and s be the distance covered by the object.

Then, according to the third law of motion,

        $v^{2} - u^{2} =2as$    ...(1)

       

In the given problem,

          $s = h_{max}$  

          $a =- g$

        (since the ball is thrown upward)

where g is the acceleration due to gravity and $h_{max}$ is the maximum height covered by the ball.

         $v = 0$

         $g = -10\ m/s^2$

         $h_{max} =90\ m$

         $u = ?$

Substitute these values into equation(1)

         $0^{2} - u^{2} =2\times-10\times 90$

         $u = 42.4264 \ m/s$