Question

a stone is dropped from the roof of a building takes 4s to reach ground. the height of the building is? ​

Answer 1

Answer:

Given: Initial velocity=0

Time taken=4 sec

Acceleration=g=10m/s^2

Using equation 2nd

s=ut+1/2at^2

s=(1/2)(10)(4)(4)

s=80

So it's given distance travelled means the height of building...

Therefore the height is 80m

Answer 2

Given :

➡Initial velocity ( u ) = 0 m/s

➡Time taken ( t ) = 4 s

➡acceleration due to gravity ( g ) = 9.8 m/s²

To Find :

➡Height of the building = ?

Solution :

Using second equation of motion

$\large\fbox{ \bold{ \large{s = ut + \frac{1}{2} \: \times a {t}^{2} }}}$

$\to s = 0 \times 4 + \frac{1}{2} \times 9.8 \times {(4)}^{2} \\ \\ \to s = \frac{1}{2} \times 9.8 \times 16 \\ \\ \to s = \frac{98}{10} \times 8 \\ \\ \to s = \frac{98}{5} \times 4 \\ \\ \to s = 19.6 \times 4 \\ \\ \to s = 78.4 \: \: m \:$

Therefore , 78.4 meter is the height of the building