Question

A ball bearing took 20.9ˍs to fall when dropped from a helicopter. From what height was the ball bearing dropped?

Answer 1

$\boxed{ \bf{Given : }}$

• Time taken by a ball bearing = 20.9 seconds

• Initial velocity,u = 0 m/s [ Body starts from rest ]

• Acceleration due to gravity,g = 9.8 m/s²

$\boxed{ \bf{To \: be \: calculated : }}$

From what height was the ball bearing dropped?

$\boxed{ \bf{Solution : }}$

By using second equation for freely falling body, we get:

$\sf{h = ut + \frac{1}{2} gt {}^{2} }$

Substituting the values..

$\sf\rightarrow \: h = 0 \times 20.9 + \dfrac{1}{ \cancel{2}} \times \cancel{9.8} \times 20.9$

$\sf \rightarrow \: h = 0 + 4.9 \times 20.9$

$\sf \rightarrow \: 102.41 \: m \: (approx)$

$\bf \therefore \: Height \: is \: 102.41 \: m$