projectile angle

diaagr16 · #1 Jun 22, 2008, 11:19 AM

a particle is thrown over a triangle from one end of a horizontal base and gauging the vertex falls on other end of the base .if a and b are base angles and c the angle of projection, prove that
tan c = tan a + tan b

ebaines · Jun 23, 2008, 12:10 PM

I think you mean "grazing the vertex," not "gauging" - right?

This is essentially a math probem -- the ony physics here is in recognizing that the path taken by the thrown particle is a parabola. Let's call the length of the base B, and the maximum height of the parabola H. If we center the parabola on the y-axis, its equation is:

$<br /> y-h = -\frac {4H} {B^2} x^2<br />$

The tangent of angle "a" is $\frac y {(B/2+x)}$ and the tangent of angle "b" is $\frac y {(B/2-x)}$ . You want to show that the sum of tan(a) and tan(b) is the derivative of the parabola at x = -b/2, which is equal to tan(c). Can you take it from here?



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