What height was it thrown from.

  • #1
theshanthan
3
0

Homework Statement



A certain freely falling object requires 1.20 s to travel the last 34.0 m before it hits the ground. From what height above the ground did it fall?

Homework Equations



v = v + at




The Attempt at a Solution



I really tried to do it in my notes and it is a mess. It is more of a conceptual thing, but I just cannot figure out what to do. I read and re-read the question so many times, but I am not able to figure it out.

Please answer as fast as possible as it a test between my friend who asked this question on cramster(a paid service) and me. I want the world to be free.
 
Last edited:

Answers and Replies

  • #2
Mindscrape
1,861
1
Okay, well, you probably aren't going to get much help in the future when you tell people you're exploiting their time so you can prove a point to a friend. Anyway, since I know that you truly came to learn physics, and I believe more people should have fun with physics I will help you...

The problem tells you that the last 34m takes 1.2s. We should be able to assume that the object is dropped (has no initial downward velocity) and we need to find the point where it was dropped.

So, I would first see how fast the object was moving at the point 34m above ground with the kinematic equation
y2-y1=v0*t+.5gt^2

That gives you the velocity the object started at 34m above ground. Then you can use the equation
v^2=v0^2+2a(y4-y3)
to go further back and see how far the object must have traveled to get that velocity.

I'll let you figure out the final answer on your own as I think I've given you more than enough of a push in the right direction. Also, this is just one of many ways to solve this problem, so you may see some alternatives.
 

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