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Projectile: Find initial velocity without time

by JJBladester
Tags: angle, projectile, time, velocity
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JJBladester
#1
Sep11-10, 11:25 AM
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1. The problem statement, all variables and given/known data
Knowing that snow is discharged at an angle of 40 degrees, determine the initial speed, v0 of the snow at A. Answer: 6.98 m/s


2. Relevant equations





3. The attempt at a solution

I have found the x and y velocity and position formulas. Now since I don't know time, should I solve both position equations for time (t) and set them equal to each other to get my only unknown, vi? The quadratic equation for time in the y-dir seems a bit hectic. Is there an easier way to go about trying to find vi?
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kuruman
#2
Sep11-10, 09:25 PM
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Start with
L = v0 t cosθ
Δy = v0 t sinθ - (1/2) g t2

Solve the first equation for t and replace in second equation. Solve the ensuing equation for v0.
JJBladester
#3
Sep12-10, 07:47 AM
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Quote Quote by kuruman View Post
Start with
L = v0 t cosθ
Δy = v0 t sinθ - (1/2) g t2

Solve the first equation for t and replace in second equation. Solve the ensuing equation for v0.
I believe this is what you had in mind. The answer matches the professor's answer. Thanks again kuruman!



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