Question

A rock is dropped at the same instant that a ball at the same initial elevation is thrown horizontally. which will have the greater speed when it reaches ground level?

Answer 1

Answer:

 If we consider vertical velocity both have same vertical velocity of $\sqrt{2gH}$

  Resultant velocity when stone hits the ground is more for thrown horizontally.

Explanation:

We have equation of motion, $v^2=u^2+2as$, where u is the initial velocity, u is the final velocity, s is the displacement and a is the acceleration.

When rock is dropped:

    Initial velocity = 0 m/s , displacement = H and acceleration = g.

    $v^2=0^2+2gH\\ \\ v=\sqrt{2gH}$

 When rock is thrown horizontally:

    Considering vertical motion of rock

       Vertical initial velocity = 0 m/s ,Vertical displacement = H and vertical acceleration = g.

    $v^2=0^2+2gH\\ \\ v=\sqrt{2gH}$

 If we consider vertical velocity both have same vertical velocity of $\sqrt{2gH}$

 But stone thrown horizontally will have horizontal velocity also, so it has more velocity if we compare resultant velocity.