- #1
jal3ous
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Homework Statement
A projectile is thrown from a point A on an inclined plane field of unknown slope α, and hits the field on a point B. We know the angle between the initial velocity and the field: θ. We know the magnitude of the velocity: V. We know the the acceleration of gravity: g. We know the slant range of the projectile (distance between A and B): R. We have no friction.
Calculate α in terms of θ,V,g, and R.
I worked on this problem and I always get a complex 4th degree polynomial equation or a trigonometric equation that I can't figure out how to solve.
Homework Equations
V sin(alpha + theta)t = R sin(alpha)
V cos (alpha+theta)t + (1/2)gt^2 = R cos(alpha)
The Attempt at a Solution
Consider alpha the angle between the gravity vector and the field. Consider a 2D reference frame (X,Y) that contains the trajectory and let Y be vertical and opposite to g and X be horizontal and such that the trajectory is in X > 0. if we decompose the equation of motion along X we get: V sin(alpha + theta)t = R sin(alpha). along Y we get: V cos (alpha+theta)t + (1/2)gt^2 = R cos(alpha). if we divide the second equation by the first we get a trigonometric equation with cot(alpha+theta), sin(alpha+theta), and cot(alpha). I couldn't go any further from here