Negative angle projectiles

In summary: Assuming that the angle is fixed, then the initial speed and angle after the bounce can be found using the Pythagorean theorem.
  • #1
Eube
3
0

Homework Statement


Trying to work out final velocity of a projectile that is initially fired at a negative angle. Initial velocity is 30m/s at a negative angle of 16 degrees. Initial height is 0.44m. Can't get my head around the initial horizontal velocity. I figure its Vox =30 sin 16 =28.8m/s. What's Voy? Its not just gravity because its fired at an initial speed. How do you combine them?


Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
  • #2
Eube said:

Homework Statement


Trying to work out final velocity of a projectile that is initially fired at a negative angle. Initial velocity is 30m/s at a negative angle of 16 degrees. Initial height is 0.44m. Can't get my head around the initial horizontal velocity. I figure its Vox =30 sin 16 =28.8m/s. What's Voy? Its not just gravity because its fired at an initial speed. How do you combine them?

Hi Eube, welcome to Physics Forums.

Did you make a drawing of the scenario? The X and Y components of the velocity can be found by applying the usual Vx = V cos(θ) and Vy = V sin(θ) method.

Remember that gravitational acceleration applies only to motion in the vertical direction. Acceleration starts once the projectile is in motion, in this case once it has its initial velocity.
 
  • #3
The attached image shows the problem. Basically its a ball being fired at 30m/s at a downward angle of 16 degrees. It is fired at a distance of 1.6m away from the intended target. I am trying to work out the height it needs to be fired at? My thinking is that it won't be a straight path due to gravity acting on it so the height will be higher than if it was a constant velocity along the path. So the height needs to be increased slightly to compensate for gravity. Just not sure how to account for that.

I am trying to find the angle and path the ball will follow after it bounces. Ball mass = 0.057kg coefficient of restitution = 0.7. I figure I just need to know the final velocity when the ball hits the ground and the angle will still be 16 degrees which can be used to find the initial speed and angle after it bounces.
 

Attachments

  • projectilebounce.jpg
    projectilebounce.jpg
    7.7 KB · Views: 584
Last edited:
  • #4
Eube said:
The attached image shows the problem. Basically its a ball being fired at 30m/s at a downward angle of 16 degrees. It is fired at a distance of 1.6m away from the intended target. I am trying to work out the height it needs to be fired at? My thinking is that it won't be a straight path due to gravity acting on it so the height will be higher than if it was a constant velocity along the path. So the height needs to be increased slightly to compensate for gravity. Just not sure how to account for that.

Is the firing angle fixed at 16° below the horizontal, or is the impact angle that is 16°? Your diagram seems to indicate the latter, but your previous post stated the former...
You're right that the projectile path is going to be curved; in fact it'll be a section of a parabola; the launch and landing angles will not be the same in general. So the firing height is not predetermined. Is the horizontal distance from the firing point to the target (1.6m) fixed?
I am trying to find the angle and path the ball will follow after it bounces. Ball mass = 0.057kg coefficient of restitution = 0.7. I figure I just need to know the final velocity when the ball hits the ground and the angle will still be 16 degrees which can be used to find the initial speed and angle after it bounces.

Depending upon what are truly your fixed parameters, the remaining conditions should be solvable. The 16° incidence angle needs to be clarified.
 
  • #5


I would like to first clarify that negative angles in projectile motion refer to angles below the horizontal line. In this case, the initial vertical velocity (Voy) would be negative as it is directed downwards.

To combine the horizontal and vertical components of the initial velocity, we can use the Pythagorean theorem. The initial horizontal velocity (Vox) and initial vertical velocity (Voy) form a right triangle, with the initial velocity (Vo) as the hypotenuse. Therefore, we can use the equation Vo^2 = Vox^2 + Voy^2 to solve for Voy.

In this case, using the given information, we can calculate Voy as follows:

Vo = 30 m/s
Vox = 30 sin 16 = 8.1 m/s (rounded to one decimal place)
Voy = √(Vo^2 - Vox^2)
= √(30^2 - 8.1^2)
= √(900 - 65.61)
= √834.39
= 28.9 m/s (rounded to one decimal place)

Therefore, the initial vertical velocity (Voy) is approximately -28.9 m/s, indicating that the projectile is initially moving downwards. It is important to note that this is the magnitude of the velocity, and the negative sign indicates its direction.

I hope this helps to clarify the confusion regarding combining the horizontal and vertical components of the initial velocity in negative angle projectiles.
 

1. What is a negative angle projectile?

A negative angle projectile is an object that is launched into the air at an angle below the horizontal. This means that the object will travel downwards as it moves forward.

2. How does the angle affect the trajectory of a projectile?

The angle at which a projectile is launched affects its trajectory or path. A negative angle will result in a downward trajectory, while a positive angle will result in an upward trajectory. The steeper the angle, the higher the projectile will go before reaching its target.

3. What is the maximum range of a negative angle projectile?

The maximum range of a negative angle projectile is determined by the angle of launch and the initial velocity. A lower angle will result in a shorter range, while a higher angle will result in a longer range. The maximum range is achieved when the projectile is launched at a 45 degree angle.

4. What factors can affect the distance traveled by a negative angle projectile?

The distance traveled by a negative angle projectile is affected by several factors, including the angle of launch, initial velocity, air resistance, and gravity. These factors can impact the trajectory and ultimately the distance traveled by the projectile.

5. How is the motion of a negative angle projectile calculated?

The motion of a negative angle projectile can be calculated using the principles of physics, specifically kinematics. These calculations take into account the angle of launch, initial velocity, and acceleration due to gravity to determine the projectile's trajectory and distance traveled.

Similar threads

  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Introductory Physics Homework Help
Replies
5
Views
229
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
11
Views
689
Replies
2
Views
2K
Replies
3
Views
3K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
3
Views
387
  • Introductory Physics Homework Help
2
Replies
38
Views
1K
Replies
5
Views
2K
Back
Top