Question

A boy throws a ball vertically upward with a velocity of 72 km/hr. After how much time will the ball return to his hand? Also find the height covered by the ball.​

Answer 1

Answer:

Time taken to reach the hand= 4secs

Maximum height= 20m

Explanation:

we have,

initial velocity= 72km/h = 20m/s

final velocity= 0m/s

time taken to reach maximum height=?

maximum height=?

acceleration=acceleration due to gravity=g=10m/s²

So, with the above information let's put the first equation of motion.

v=u+at

=> 0=20+(-10)(t)

=>10t=20

=> t=2secs

So, it takes 2secs for its ascent to reach the maximum height. So it will also take 2secs for its decent. So the time taken to reach the hand is 4secs.

Now, let's calculate the maximum height reached.

Let's put the third equation of motion.

v²=u²+2as

=> 0=(20)²+2(-10)(s)

=> 400=20s

=> s=400/20=20m

So the maximum height reached is 20m