Projectile motion rock off a cliff

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SUMMARY

The discussion focuses on solving a projectile motion problem involving a rock thrown off a cliff at an initial velocity of 18 m/s at a 17-degree angle below the horizontal. The key equations used are Vf = Vi + at and change in Y = Vit + 0.5at². A participant struggled with obtaining a negative time value of -3.87 seconds, indicating a miscalculation. The solution involves eliminating time by relating the horizontal displacement to the vertical displacement using appropriate kinematic equations.

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  • Familiarity with kinematic equations
  • Basic trigonometry for angle calculations
  • Knowledge of horizontal and vertical displacement relationships
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  • Learn how to resolve vectors into horizontal and vertical components
  • Practice problems involving kinematic equations in two dimensions
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Students studying physics, particularly those focusing on kinematics and projectile motion, as well as educators seeking to enhance their teaching methods in these topics.

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Homework Statement


A rock is thrown down off a cliff at 18 m/s at an angle of 17 below the horizontal. If the rock hits a cliff that is 16m away, how far down did the rock fall.


Homework Equations


Vf= Vi + at
change in Y= Vit + .5at^2


The Attempt at a Solution


I tried solving for time and then plugging that back into the equations and I kept getting -3.87. Please help!
 
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You can eliminate time by writing an equation for the x displacement of the rock and subbing this into your equation for it's y displacement.
 

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