# d. An object thrown vertically upwards reaches a height of 500 m. What was its initial velocity?

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d. 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

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the final velocity is zero. We know the position is 500 and acceleration is 10

Let the initial velocity = u
final velocity = v
v= 0 m/s
s = 500 m

$$2gs=v^2-u^2$$

$$u^2= 2(10)500$$ --{square root of negative }

$$u=100m/s$$

v = u + at

0 = 100 - 10 t

t = 10 s

Since it took 10 secs to go up it would take tens secs to go down thus giving us a total travel time of 20 secs.

Answer is 100 m/s 20 s