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Projectile Question ,,

  • Thread starter Lord Dark
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  • #1
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Homework Statement


Hi everyone ,, yesterday I had an exam with the following question :
A ball is vertically thrown from a height (h) then it collide with the ground and went to height (5+h), the whole time of the projectile is 2 seconds .

(a) Find the initial velocity and the time it took until it reached the ground.
(b) Find (h) and the velocity before hitting the ground

Homework Equations





The Attempt at a Solution


The question was really hard ,, I didn't really know how to solve it .. I applied the following :
t1+t2=2 ,, and t1 (the time until it reached the ground) and t2(the time until it reached the height (h+5) , the equation of t1 (h=Vot1+0.5*g*t1^2) and for t2 (5-h=(V+gt1)t2-0.5*g*t2^2) and I combined them together and got V=7.5 m/s .. is it right ?? .. is the attempt to solve is even right ??
 

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Answers and Replies

  • #2
LowlyPion
Homework Helper
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Can't see the picture.

Is the ball thrown initially downward? That's what your equations reflect.
 
  • #3
LowlyPion
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... and for t2 (5-h=(V+gt1)t2-0.5*g*t2^2) and I combined them together and got V=7.5 m/s .. is it right ?? .. is the attempt to solve is even right ??
That doesn't look quite right.

Wouldn't it be more like

h + 5 = (V0 +g*T1)*T2 - 1/2*g*T22

Is the 5 - h a typo ?
 
  • #4
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it's true ,, it's h+5 ,, but can you tell me what is the answer you got ,, I just wanna know if my answer is right or wrong
 
  • #5
LowlyPion
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it's true ,, it's h+5 ,, but can you tell me what is the answer you got ,, I just wanna know if my answer is right or wrong
Sorry I didn't solve it. It looks a little tedious.
 
  • #6
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it took me 1:30 hour in the exam and am still not sure if it's right or wrong -_-
 
  • #7
LowlyPion
Homework Helper
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it took me 1:30 hour in the exam and am still not sure if it's right or wrong -_-
Well, you'll find out soon enough then. It's not like you can change it now.

Good luck.
 

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