The Cliff Diver - Projectile motion

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Homework Help Overview

The problem involves a swimmer diving off a cliff with a horizontal leap, aiming to determine the minimum speed required to clear a ledge below. The context is projectile motion, specifically analyzing horizontal and vertical components of motion under gravity.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply kinematic equations to relate horizontal distance and vertical drop, but expresses uncertainty in progressing from their calculations. Some participants suggest solving for time first and substituting it into the equations to find the initial speed.

Discussion Status

Participants have engaged in calculations and shared results, with one confirming their approach appears correct. There is a suggestion to clarify the treatment of signs in the equations, indicating an ongoing exploration of assumptions regarding direction in the problem.

Contextual Notes

There is mention of potential scrutiny from a marker regarding the treatment of signs in the equations, highlighting the importance of clarity in assumptions about direction in projectile motion.

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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