Finding Velocity via Convervation of Energy

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SUMMARY

The discussion focuses on calculating the speed of a projectile when it strikes the ground using the conservation of energy principle. The projectile is launched from a cliff at an angle of 25 degrees with an initial velocity of 195 m/s from a height of 315 m. The correct approach involves equating the initial energy, which is calculated using the formula 0.5 * m * (195^2), to the final energy, represented as 0.5 * m * (final velocity^2). The mass cancels out, and the final velocity is determined to be approximately 114 m/s, highlighting the importance of using the correct initial velocity without decomposing it into components for this energy-based problem.

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Homework Statement


A projectile is shot upward from the top of a cliff in an angle of 25 with a velocity of 195 m/s.The height of the cliff is 315m. What will be its speed when it strikes the ground below? (Use conservation of energy)



Homework Equations


Ok...initial energy = final energy

Initial energy = .5m*(initial velocity square) + mgy
Final energy = .5m*(final velocity square)

initial velocity = sin*theta*upward initial velocity = sin25*195


The Attempt at a Solution



So I set them to equal and I got final V to be 114, but it says I had it wrong, canceling out the mass... I have no clue what I did wrong there...
 
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initial velocity = sin*theta*upward initial velocity = sin25*195
should not be used in this one. It is an energy problem, not a 2D motion analysis. Just use the 195 in the first 1/2m*v^2.
 
Delphi51 said:
should not be used in this one. It is an energy problem, not a 2D motion analysis. Just use the 195 in the first 1/2m*v^2.

OK, thank you! =)
 

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