Question

A ball thrown upwards attains a maximum height of 20m.Find the velocity with which it was thrown.(Take g= 10m/s2)

Answer 1

Explanation:

Let the velocity of projection is u, and the final velocity at the top height will be zero.

The velocity of the projection is given as,

v

2

=u

2

−2gh

u=

2×10×45

u=30m/s

The time when the velocity of ball become to half velocity of projection is given as,

v=u−gt

15=30−10×t

t=1.5s

Thus, the time when the velocity of ball become to half velocity of projection is 1.5s.

Answer 2

Given,

• Height = 20m
• g= 10m/s2

To find,

The velocity

Solution,

We have to solve the following problem by applying some physics fundamentals,

First, we will find the velocity of the projection,

Let the velocity of projection be u, and the final velocity at the top height will be zero.

The velocity of the projection is given as,

⇒v2=u2−2gh

⇒u= 2×10×45

⇒u=30m/s

Second, we will find out the time required

The time when the velocity of the ball becomes to half velocity of projection is given as,

⇒v=u−gt

⇒15=30−10×t

⇒t=1.5s

Hence, the time when the velocity of the ball becomes half the velocity of projection is 1.5s.