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Author Topic: Projectile Motion Questions  (Read 2311 times)  Share 

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kaanonball

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Projectile Motion Questions
« on: January 20, 2009, 09:05:19 pm »
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1.) A water skier at the Moomba Masters competition in Melbourne leaves a ramp at a speed of 50km/h and at an angle of 30 degrees. The edge of the ramp is 1.7m above the water. Calculate:

(a) the range of the jump [answer = 18m]
(b) the velocity at which the jumper hits the water. [answer = 15m/s at 37 degrees to the horizontal]

2.) A gymnast wants to jump a distance of 2.5m, leaving the ground at an angle 28 degrees. With what speed must the gymnast take off? [answer = 5.5m/s]

any help would be appreciated =]
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pHysiX

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Re: Projectile Motion Questions
« Reply #1 on: January 21, 2009, 11:16:54 am »
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Can't figure out question 1 yet but got question 2:

Let the velocity be x:
The vertical velocity would be xsin28 and the horizontal would be xcos28.

Now, we must find the total airborne time:
v=u+at
0= xsin28 - 10t
t= (1/10)xsin28

Hence, total airborne time is (1/5)xsin28 seconds

Now we know the range of the jump is 2.5m and it is constant horizontal velocity
Therefore:
d=vt
2.5=xcos28 * (1/5)xsin28
x^2 = 12.5/(cos28 * sin28)
x= 5.49m/s

Two s.f. ==> 5.5m/s

Sorry...i'm a bit n00b with latex =]
« Last Edit: January 21, 2009, 11:40:49 am by pHysiX »
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bubble sunglasses

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Re: Projectile Motion Questions
« Reply #2 on: January 21, 2009, 01:40:38 pm »
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 check out 6th and 7th replies
 http://community.boredofstudies.org/421/physics/136267/projectile-motion-question.html


  sorry, couldn't resist ;)
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pHysiX

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Re: Projectile Motion Questions
« Reply #3 on: January 21, 2009, 02:07:49 pm »
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ROFL HILARIOUS!
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IntoTheNewWorld

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Re: Projectile Motion Questions
« Reply #4 on: January 21, 2009, 03:49:55 pm »
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Dammit I keep getting 19m range for 1 a)

Sigh at physics
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kaanonball

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Re: Projectile Motion Questions
« Reply #5 on: January 21, 2009, 04:18:15 pm »
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kurrymuncher

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Re: Projectile Motion Questions
« Reply #6 on: January 21, 2009, 04:41:19 pm »
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ROFL Enwiabe was so funny on BoS
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Mao

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Re: Projectile Motion Questions
« Reply #7 on: February 04, 2009, 10:14:24 pm »
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First question:

a)

initial horizontal velocity:

initial vertical velocity:
time to maximum:
vertical displacement:
vertical distance (at maximum):

time to drop to zero:

time (total):

displacement (horizontal):

b)
vertical velocity on landing:

speed on landing:

angle to horizontal:


I think the answer given by the book is incorrect for part a)
« Last Edit: February 04, 2009, 10:26:40 pm by Mao »
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dejan91

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Re: Projectile Motion Questions
« Reply #8 on: February 08, 2009, 11:17:45 pm »
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LOL I had no idea how to put equations up on the forum...so my apologies if its unreadble or whatever.
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dejan91

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Re: Projectile Motion Questions
« Reply #9 on: February 08, 2009, 11:23:37 pm »
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^^Note that's the long way just to show HOW to get the answer. You could also use the range formula (which I'll post when I find).
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Mao

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Re: Projectile Motion Questions
« Reply #10 on: February 08, 2009, 11:50:22 pm »
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(assuming the height of projection and landing are the same)
« Last Edit: February 08, 2009, 11:54:34 pm by Mao »
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dejan91

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Re: Projectile Motion Questions
« Reply #11 on: February 09, 2009, 03:59:36 pm »
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Yup that's the one I was looking for. Much quicker way.
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