Question

A body projected vertically up with a velocityof 10m/
s reaches a height of 20m. If it is projected with a
velocity of 20m/s, then the maximum height reached
by the body is​

Answer 1

Given :-

A  body projected vertically up with a velocity of 10m/ s reaches a height of 20m. If it is projected with a  velocity of 20m/s,

To Find :-

Maximum height

Solution :-

We know that

v² - u² = 2gh

Here

v = 0

u = 10

h = 20

(0)² - (10)² = 2(-g)(20)

0 - 100 = -40g

-100/-40 = g

5/2 = g

Now

v² - u² = 2gh

Here

v = 0

u = 20

g = 5/2

(0)² - (20)² = -[2(5/2)(h)]

0 - 400 = -[5h]

-400 = -5h

400 = 5h

400/5 = h

80 = h

Answer 2

Solution :

• A body is projected vertically up with a velocity of 10 m/s.

It reaches a maximum height of 20m.

Now , if it's projected with a velocity of double the inital velocity, i.e 20 m/s , we have to find the maximum height reached by the body.

To do this, let us apply the third equation of motion

v² - u² = 2as

Here , u is the velocity its projected with , v is 0 , a is the acceleration and s is the maximum height

-u² = 2as

s = -½ u²/a

If u = 10m

20 = -½ × 100/a

>> a = 5/2

Placing the value of u as 20 m/

> -½ × 400 × 2/5

> 80 m

Answer : The maximum height reached by the body is 80m.

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