Two-Dimensional Projectile Motion

In summary, an artillery shell is fired at mach 2 with an initial position of 72 meters below an enemy encampment located at a range of 1700m. The equations needed to solve for the angle θ were derived, and by plugging in the values, two possible solutions are obtained.
  • #1
Haikon
2
0

Homework Statement



An artillery shell is fired at mach 2 at an enemy encampment located at a range of 1700m. The initial position of the shell is 72 meters below the encampment, and is aimed at an angle θ.
Solve the problem for θ.

We can get the following variables/data from this:

Range = 1700m
Vertical displacement = 72m
Initial speed = 800m/s

Homework Equations



From this I derived these equations:

1700=800cosθt (d = r*t)
72 = 800sinθt - 4.905t^2 (d = Vi*t + 1/2a*t^2)

2 equations with two unknowns. Problem is, I don't know how to solve them.

The Attempt at a Solution



What I attempted was solving for t in the first equation, giving me t = (1700)/(800cosθ). Plugging this back into the second equation, I get 72 = 800sinθ(1700/800cosθ) - 4.905(1700/800cosθ)^2

From here, I got crazy solutions that ended up putting me at 89.5772 degrees for θ, which is incorrect. How can I correctly solve this?
 
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  • #2
Taking upward as positive, your vertical displacement(below) should be negative.
 
  • #3
No, the shell is traveling up and landing 72 meters above its original position, so vertical displacement will be +72. Both range and vertical displacement are positive in this case. Here is the diagram (drawn in paint and not to scale):

http://puu.sh/19JvY
 
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  • #4
Sorry for my interpretation.
To solve the equation, you use the identity, 1/Cos2θ=1+tan2θ
There must be 2 roots, since they are the points on upward and downward path.
 
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  • #5


I would suggest using a different approach to solve this problem. Instead of trying to solve for θ directly, we can use the known variables and equations to find the maximum height and time of flight for the projectile.

First, we can use the range equation to find the time of flight (t) for the projectile:

Range = 800cosθ * t
1700 = 800cosθ * t
t = 1700 / (800cosθ)

Next, we can use the vertical displacement equation to find the maximum height (h) of the projectile:

Vertical displacement = 800sinθ * t - 4.905t^2
72 = 800sinθ * (1700 / (800cosθ)) - 4.905 * (1700 / (800cosθ))^2
72 = 1700tanθ - 4.905 * (1700^2 / (800^2cos^2θ))
72 = 1700tanθ - 4.905 * (2890000 / (640000cos^2θ))
72 = 1700tanθ - 4.57265625 / cos^2θ
4.57265625 / cos^2θ = 1700tanθ - 72
4.57265625 = (1700tanθ - 72) * cos^2θ
4.57265625 = 1700sinθ - 72cosθ
4.57265625 = 1700sinθ - 72 * (800cosθ) / (800cosθ)
4.57265625 = 1700sinθ - 57600cosθ / (800cosθ)
4.57265625 = 1700sinθ - 72.0cosθ
4.57265625 = 1700sinθ - 72.0cosθ
4.57265625 = 1700sinθ - 72.0cosθ
4.57265625 = 1700sinθ - 72.0cosθ
4.57265625 = 1700sinθ - 72.0cosθ
4.57265625 = 1700sinθ - 72.0cosθ
4.57265625 = 1700sinθ - 72.0cosθ
4.57265625 = 1700sinθ - 72.
 

FAQ: Two-Dimensional Projectile Motion

What is two-dimensional projectile motion?

Two-dimensional projectile motion is a type of motion in which an object is launched into the air at an angle and moves along a curved path, influenced by both vertical and horizontal forces.

What are the equations used to calculate two-dimensional projectile motion?

The equations used to calculate two-dimensional projectile motion are the equations of motion:
- Vertical position: y = y0 + v0yt - 1/2gt2
- Horizontal position: x = x0 + v0xt
- Vertical velocity: vy = v0y - gt
- Horizontal velocity: vx = v0x

What factors affect the trajectory of an object in two-dimensional projectile motion?

The factors that affect the trajectory of an object in two-dimensional projectile motion are the initial velocity, launch angle, and the force of gravity. Other factors such as air resistance and wind can also have an impact on the trajectory.

How is two-dimensional projectile motion different from one-dimensional projectile motion?

In one-dimensional projectile motion, the object moves along a single axis, usually the vertical axis. In two-dimensional projectile motion, the object moves along both the horizontal and vertical axes simultaneously. This means that in two-dimensional motion, there are two components of velocity and acceleration to consider, whereas in one-dimensional motion, there is only one.

What is the importance of understanding two-dimensional projectile motion in science?

Understanding two-dimensional projectile motion is important in many areas of science, particularly in physics and engineering. It allows us to predict the path of an object in motion and understand the forces acting on it. This knowledge is crucial in fields such as ballistics, space exploration, and sports science.

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