How to Solve Projectile Motion of a Stone Thrown at 30 Degrees Below Horizontal?

AI Thread Summary
The discussion focuses on solving a projectile motion problem involving a stone thrown at a 30-degree angle below the horizontal, landing 57 meters away. Key calculations include determining the time of flight, initial speed, and impact velocity angle, with the answers being 1.57 seconds, 41.9 m/s, and 51.2 m/s at -45 degrees, respectively. Participants discuss using the x-displacement equation to eliminate the initial velocity from the y-displacement equation. There is confusion regarding the appropriate value for vertical displacement in the calculations. The conversation emphasizes the importance of correctly applying kinematic equations to solve projectile motion problems.
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Homework Statement



Suppose the stone is thrown at an angle of 30 degrees below the horizontal. If it strikes the ground 57m away. find (a) the time of flight (b) the initial speed, and (c) the speed and the angle of the velocity vector with respect to the horizontal at impact. (Hint: for part (a) use the equation for the x-displacement to eliminate vot from the equation for the y-displacement.)

answers: (a) 1.57s (b) 41.9 m/s (c) 51.2 m/s, -45 degrees

Homework Equations



x final- x inital= vo cos(theta)t
y final- y initial= vo sin(theta)t- 1/2g t^2

The Attempt at a Solution



i get that vot= 57/cos(30) and i plug it into the equation for y-position but i can't get the same answer.
 
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I'm a bit curious, what value are you using for the displacement y?
 

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