Question

A stone is allowed to fall from the top of the tower reaches the ground in 8 sec. find the height of the tower

Answer 1

h=1/2 gt²

hence height =5*64=320 m

Answer 2

Explanation:

Given :-

A stone is allowed to fall from the top of a tower of height = 100 m

Acceleration due to gravity = 10 m/s²

Initial velocity of stone projected upwards = 25 m/s

To Find :-

When will the two stones meet.

Where will the two stones meet.

Solution :-

We know that,

g = Gravity

u = Initial velocity

t = Time

s = Displacement

Using the formula,

\underline{\boxed{\sf Displacement=ut+\dfrac{1}{2} gt^2}}

Displacement=ut+

2

1

gt

2

Given that,

Initial velocity (u) = 0 m/s

Gravity (g) = 10 m/s

Substituting their values,

Let the height covered by the falling stone by s₁.

⇒ s₁ = 0 × t + 1/2 (10) t²

⇒ s₁ = 10/2 t²

⇒ s₁ = 5t² ____(1)

Given that,

Gravity (g) = 10 m/s

Initial velocity (u) = 25 m/s

Substituting their values,

Let the distance covered by the stone thrown upward be s₂.

⇒ s₂ = 25t + 1/2 (-10) t²

⇒ s₂ = 25t + -10/2 t²

⇒ s₂ = 25 - 5t² ____(2)

Given that,

Total height = 100 m

By adding (1) and (2),

s₁ + s₂ = 100m

⇒ 5t² + (25t - 5t²) = 100

⇒ 5t² - 5t² + 25t = 100

⇒ 25t = 100

⇒ t = 100/25

⇒ t = 4 sec ____(3)

By substituting (3) in (1),

s₁ = 5t²

⇒ s = 5 (4)²

⇒ s = 5 (16)

⇒ s = 80 m

Therefore, the two stones will meet at a distance of 80 m after 4 sec.