The Cliff Diver - Projectile motion

AI Thread Summary
A swimmer must calculate her minimum horizontal speed to avoid a ledge while diving off a cliff that is 9.5 meters high and 1.5 meters wide. Using the equations of motion, the time of fall is determined to be approximately 1.389 seconds. Substituting this time into the horizontal motion equation yields a required speed of about 1.08 m/s. It is suggested to clarify the direction of motion in the calculations to avoid confusion with negative signs. The solution appears correct, but attention to detail in sign conventions is advised.
Bottomsouth
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Homework Statement




A swimmer dives off a cliff with a running horizontal leap. What must her minimum speed be just as she leaves the top of the cliff so that she will miss the ledge at the bottom which is 1.5 m wide and 9.5m below the top of the cliff.



Homework Equations



X=V0xT Y=-1/2gt^2

The Attempt at a Solution



I have X=1.5 and Y=9.5

9.5=-1/2*9.8*t^2
1.5=V0x*t

From there I am lost, I've tried squaring T and so on. Any help is appreciated.
 
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Solve the first equation for the time. Substitute it into the second to find the Vo.
 
9.5=-1/2*9.8*t^2
9.5=-4.9*t^2
1.93=t^2
t=1.389

1.5=Vox*1.389
1.08=Vox

Does this sound right?
 
Looks good!
In case your marker is picky, it would be a good idea to deal with the extra minus sign in the first part. Either think of "down" as positive and not use any minus signs, or put a minus sign on the 9.5 to indicate it is down.
 
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