An object thrown vertically upwards reaches a height of 500 m. What was its initial velocity ?
How long will the object take to come back to the earth ? Assume ` g = 10 m//s^(2)`

Explanation

Data : `h = 500 m , g = 10 m//s^(2)`
v= 0 m/s , u= ?, t for the object going up + t for the object coming down = ?
As the object moves upward,
` v^(2) = u^(2) + 2as = u^(2) + 2(-g)h " " (therefore a = -g)`
Now, v = 0 m/s
` u^(2) = 2gh = 2 xx 10 m//s^(2) xx 500 m`
` u^(2) = (100 xx 100) m//s^(2)`
u = 100 m/s ( initial velocity of the object)
Also, u = u + at = u - gt
For v= 0 m/s , u = gt
` 100 m//s = 10 m//s^(2) xx t " " therefore` t for the body going up = 10s
Now, t for the object coming down = t for the object going up = 10s
t for the object going up + t for the object coming down = 10 s + 10 s = 20 s
It will take 20 s for the object to come back to the earth.