Question

A particle is projected vertically up from the top of a tower with velocity 10 m/s. It reaches the ground
in 5s. Find-
(a) Height of tower.

The answer mentioned is 75m but I am confused that how is it possible?​

Answer 1

Answer:

So, let us take the distance from the tip of the tower to the highest point reached by the ball (from A to B) as S1

and, let the time taken by the ball to reach the highest point B be taken as T1

.

v=u+at

This is the formula we will be using to find the value of T1

,

We have,

v=0

(as velocity at the highest point will be zero).

u=20m/s

(given)

g=−10m/s2

(g is negative as it is against the upward force of the ball).

Now when we substitute the values in the above formula, we get,

⇒v=u−gT1

⇒0=20−10T1

⇒−20=−10T1

⇒T1=2sec

⇒s=ut+12gt2 is the formula we will be using to find the value of S1

We have,

u=20m/s

(given)

g=−10m/s2

(g is negative as it against the upward force of the ball)

T1=2

sec

Now when we substitute the values in the above formula, we get,

⇒S1=uT1−12gT12⇒S1=(20)(2)−12(10)(2)2⇒S1=40−20⇒S1=20m