Question

A boy is standing 490m above the ground on a building. An jet is flying on the mountain . Some people are sitting on a rock on that mountain. An elephant and his owner are walking on the mountain. The elephant drinks some water.. the boy throws a white ball from the building vertically down with initial velocity=0 .What time does the ball take to strike the ground?

Answer 1

Answer:

Well there is too much of irrelevant information which is not required here.

The needed information is:

A boy is standing 490m above the ground on a building. The boy throws a white ball from the building vertically down with initial velocity=0 .What time does the ball take to strike the ground?

Given: Height = 490 m, Initial Velocity = 0

To find: Time taken for hitting the ground

Using 2nd law of equation we get,

=> s = ut + 1/2 gt²

u = 0. hence we get,

=> s = 1/2 gt²

We know s = 490 and g = 9.8. Substituting them we get,

=. 490 = 1/2 ( 9.8 ) t²

=> 490 = 4.9t²

=> t² = 490 / 4.9

=> t² = 100

=> t = √100 = 10 seconds.

Hence the ball takes 10 seconds to strike the ground.

Answer 2

Here is your solution

Given

Height = 490m

initial velocity = 0

We have to find time does the ball take to strike the ground?

Using 2nd law of equation. we get:-

s = ut+1/2gt^2
s=0×t+1/2gt^2
s=1/2gt^2
490=1/2×10×t^2
490/5=t^2
$time = 98 \sqrt{2} second$

$time = 7 \sqrt{2}s \\or 9.89s \\time=(10 second\: approx)$
hope it helps you