• Support PF! Buy your school textbooks, materials and every day products Here!

Finding the Angle in Projectile Motion

  • #1

Homework Statement



Hello, I am attempting to derive an equation for some pretty specific needs. The equation I need is one that solves for the angle needed to launch a projectile at a given velocity to an object at a given distance and height different from launcher. The catch is that I would like to include the acceleration due to air resistance (which I can find later and input) as an acceleration in the x direction.

The goal is to solve for theta (I will use an o)

Homework Equations



The only variables that can be present in the equation are:
ax, ay (gravity), x, y, v (velocity launched at, actually, it is the speed, I don't know the angle)

The equations I have been attempting to use are:

y = vy*t + (g/2)*t^2
x = vx*t + (a/2)*t^2
v = sqrt(vx^2 + vy^2)
sin o = vy/v
cos o = vx/v


The Attempt at a Solution



I keep trying to derive but keep ending up circling (deriving until I accidentally reach a variable I tried to get rid of earlier). Does anyone have an equation already derived they could show me that they could also explain how they derived, or know how I could go about deriving my goal equation successfully? Or any other formulae I should be using?

Thanks.
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
25,832
249
Welcome to PF!

The equation I need is one that solves for the angle needed to launch a projectile at a given velocity to an object at a given distance and height different from launcher.

The catch is that I would like to include the acceleration due to air resistance (which I can find later and input) as an acceleration in the x direction.

The equations I have been attempting to use are:

y = vy*t + (g/2)*t^2
x = vx*t + (a/2)*t^2
v = sqrt(vx^2 + vy^2)
sin o = vy/v
cos o = vx/v
Hi Robotics 1764! Welcome to PF! :smile:

(air resistance would never be like that, but anyway …)

Hint: since you have constant acceleration in both the x and y directions, try combining them (accelerations obey the vector law of addition, of course) into a single acceleration, and then use coordinates parallel and perpendicular to that direction. :wink:
 

Related Threads for: Finding the Angle in Projectile Motion

  • Last Post
Replies
20
Views
7K
Replies
3
Views
28K
Replies
5
Views
13K
Replies
6
Views
8K
Replies
5
Views
36K
Replies
3
Views
4K
Replies
2
Views
8K
Replies
2
Views
7K
Top