Acceleration and free fall problem

AI Thread Summary
Rachel drops from a height of 5 meters, and the problem requires calculating the time it takes to hit the water and her final velocity upon impact. The relevant equations of motion indicate that with an initial velocity of zero and a constant acceleration of -9.8 m/s², the time to reach the surface is approximately 1.10 seconds. At the moment before hitting the water, Rachel's velocity is calculated to be -9.9 m/s. The discussion emphasizes the importance of using kinematics equations to derive these values accurately. Understanding the initial conditions and acceleration is crucial for solving free fall problems effectively.
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Homework Statement


Rachel drops straight off a high dive whose board is 5 meters above the surface of the water. How long does it take Rachel to hit the surface of the water? How fast is Rachel traveling when she hits the surface of the water?


Homework Equations





The Attempt at a Solution


I made an x vs. t graph, a v vs. t graph, and an a vs. t graph.
My variable list is as follows:

x at time 0(initial location)=5m
x(location) at end time=0m
initial velocity= is unknown
Velocity at end=0m/s
time=is unknown
acceleration=-9.8m/s^2 (which is free fall)
 
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The graphs, although conceptual, do little to help you get into the meat of the equations. Review your core kinematics equations, and choose which ones contain the variables you need to solve for.

Also, her initial velocity is zero (she starts from rest, and drops straight down). Her velocity the moment before she hits the water is the one you want to solve for.
 
Would my answers to these questions for this problem be correct:
How long does it take Rachel to hit the surface of the water?
1.10 sec

How fast is Rachel traveling when she hits the surface of the water?
-9.9m/s
 
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