Question

A cannonball is launched from the ground at an angle of 30 degrees above the horizontal and a speed of 30 m/s. Ideally (no air resistance) the ball will land on the ground with a speed of

Answer 1

As we know that here no air resistance while ball is moving in air

So here we will say that

initial total energy = final total energy

$KE_i + U_i = KE_f + U_f$

here we know that

$Ui = U_f = 0$ (as it will be on ground at initial and final position)

so we will say

$KE_i = KE_f$

since mass is always conserved

so we will say that final speed of the ball must be equal to the initial speed of the ball

so we have

$v_f = v_i = 30 m/s$

Answer 2

Answer:

When ball hits the ground its velocity will be 30 m /sec

Explanation:

We have given that there is no air resistance

So from energy conservation initial energy will be equal to final energy

So $U_I+KE_I=U_F+KE_F$

As the ball is initially at the ground and finally also on the ground

So $U_I=U_F=0$

As we know that mass is also conserved

So initial velocity will be equal to final velocity

So when ball hit the ground its velocity will be 30 m /sec