Projectile Motion Archery Problem

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SUMMARY

The discussion focuses on calculating the initial velocity of an arrow shot parallel to the ground, landing 61.0 meters away at a 3.00-degree angle. The user initially misapplied the equations of motion, particularly using the wrong components for vertical displacement. The correct approach involves using the horizontal velocity component and the equations v_f = V_h tan(3) and distance = speed * time to derive the accurate initial velocity, which is 107 m/s.

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  • Understanding of projectile motion principles
  • Familiarity with kinematic equations
  • Basic trigonometry, specifically tangent functions
  • Knowledge of gravitational acceleration (9.8 m/s²)
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Hey guys, i realize this question has been asked on these forums before, and i have seen those posts, but they don't make sense to me, and this question is on my test tomorrow so i really need to figure it out.

Homework Statement



You are watching an archery tournament when you start wondering how fast an arrow is shot from the bow. Remembering your physics, you ask one of the archers to shoot an arrow parallel to the ground. You find the arrow stuck in the ground 61.0 m away, making a 3.00 degree angle with the ground.

So distance in the x direction is going to be 61m
and you have an angle theta that is 3 degrees

Homework Equations



v_f = V_i + at [eq1]
61tan3 = height that the arrow was initially fired from (i think this is where I am wrong)
d = V_i * t + 0.5at^2 [eq2]
Y_f = Y_i + V_iy * t + 0.5 * a_y * t^2 [eq3]
distance = speed*time [eq4]

The Attempt at a Solution



so i got that 61tan3 = 3.197
I used this value in [eq3] as my y_i so i got
0 = 3.197 + 0 + 0.5(-9.8)t^2 and i solved for t which ended up being 0.8077s
then i plugged my time into [eq4] like so 61 = 0.877 * V and got 75.52 m/s for my velocity. But the answer to this problem is 107. What am i doing wrong?
 
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The angle is formed by the horizontal and final vertical velocity components not the displacement components.

V_f = V_h tan 3

Where I use V_h for the constant horizontal velocity you wish to find.

You'll need to use eq1 and eq4.

That should be a big enough hint I hope.
 

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