physics help

ok, so i am trying to study for my next years classes, and one of them is physics. I am not sure about a certain question, can any one help me?

A happy graduate throws her cap into the air. It comes back to her hand (at the same height) in exactly 2.0 seconds. With what velocity did she originally throw the cap? Assume the acceleration due to gravity is
10 m
s2

here are the choices for answers.
A)
5 m
s

B)
10 m
s

C)
15 m
s

D)
20 m
s



I think that it is B, but not quite sure.

Hello allsmiles

Quote:

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Originally Posted by allsmiles

ok, so i am trying to study for my next years classes, and one of them is physics. I am not sure about a certain question, can any one help me?

A happy graduate throws her cap into the air. It comes back to her hand (at the same height) in exactly 2.0 seconds. With what velocity did she originally throw the cap? Assume the acceleration due to gravity is
10 m
s2

here are the choices for answers.
A)
5 m
s

B)
10 m
s

C)
15 m
s

D)
20 m
s



I think that it is B, but not quite sure.

---

We must ignore air-resistance here, if we're going to solve this problem, and assume that the cap accelerates at 10 m per sec per sec downwards throughout.

If the cap takes 2 sec to come back to her hand, then it must take 1 sec to come to rest before returning in 1 further second. So, since the acceleration (downwards) is 10 m per sec per sec, the initial speed must have been 10 m per sec.

So you're right - the answer is B.

Grandad