Finding Projectile Motion range at an angle?

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Homework Help Overview

The problem involves analyzing the range of a projectile launched from a ramp on a hill, considering the angles of the ramp and the hill. The original poster has reworded the problem for clarity and is seeking to derive a specific equation for the range of the cannonball as it travels up the slope.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the use of motion equations and trigonometry to analyze the projectile's trajectory. The original poster expresses confusion about incorporating the slope of the hill into their calculations. Others suggest considering the intersection of a straight line with a parabola and relate the x and y values to the slope's tangent.

Discussion Status

The discussion is active, with participants exploring different methods to approach the problem. The original poster has made progress in finding an equation for time and is close to deriving the desired range equation, although there is uncertainty regarding the cosine factor related to the hill's slope. Guidance has been provided, indicating that the relationship between the x-value and the distance along the hill is crucial.

Contextual Notes

The original problem's wording is noted as confusing, and there is an emphasis on deriving the range specifically for the projectile's motion along the hill rather than on a flat surface. The participants are navigating the complexities of trigonometric relationships in this context.

Kavorka
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The original problem has very confusing wording without the picture so I reworded it for simplicity:

A toy cannon is placed on a ramp on a hill, pointing up the hill. With respect to the x-axis the hill has a slope of angle A and the ramp has a slope of angle B. If the cannonball has a muzzle speed of v, show that the range R of the cannonball (as measured up the hill, not along the x-axis) is given by:

R = [2v^2 (cos^2 (B))(tan(B) - tan(A))] / [g cos(A)]

The base equation we've derived for projectile range on a flat surface:
R = (v^2 /g)sin(2θ­)
from the parabolic equation:
y = vt + (1/2)at^2 (where v is initial velocity, and v and a are in the y-direction)
and setting y to 0.

I'm not completely sure how to correctly start this problem or how to properly take the angle of the slope of the hill into account, the trig is a bit overwhelming. Even a good shove in the right direction would help immensely!
 
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You are looking for an intersection of a straight line with a parabola. Do you know howto find it?
 
Yes, but were not analyzing it graphically we're analyzing it with motion equations and trig. Since I posted I was able to find an equation for time by finding the x and y-values of where the cannonball lands in terms of motion equations and relating them with the tangent of the slope of the hill, and solving for time. I then plugged T into Range = initial x velocity * time and combined the terms. My answer comes out to exactly what the original equation I want to derive is except it is over the term [g] not [g cos(A)]. I'm not sure where that cosine of the slope of the hill comes from.
 
You found the value of ##x## where the ball touches the hill. Well done! But you are asked to find the distance along the hill. It is very simply related with the the x-value you found. You are just a step away from the correct answer.
 

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