Why Did the Projectile Hit Miley Cyrus Despite Her Fall?

Click For Summary

Homework Help Overview

The discussion revolves around a kinematics problem involving a projectile and a falling object, specifically a scenario where a projectile is fired at a person (Miley Cyrus) who suddenly falls from a tree. Participants are exploring the implications of projectile motion and the timing of the fall in relation to the projectile's trajectory.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants are questioning the ambiguity of the phrase "fired upon her" and whether the projectile was aimed considering her movement. There are discussions about the nature of projectile motion and how gravity affects both the projectile and the falling object. Some participants are analyzing the timing and trajectory of the projectile in relation to Miley's fall.

Discussion Status

The discussion is ongoing, with various interpretations being explored. Some participants offer insights into the physics of the situation, suggesting that if the projectile is aimed directly at the initial position of the falling object, it may still hit the target due to the nature of parabolic motion. There is no explicit consensus yet, as different viewpoints are being considered.

Contextual Notes

Participants note the lack of specific information regarding the setup of the shot and the assumptions made about the projectile's trajectory and the timing of the fall. The original poster mentions that the teacher indicated the projectile is not fired directly below Miley, which adds to the ambiguity of the problem.

VoyagerOne
Messages
2
Reaction score
0
On a test today I came across a rather ridiculous question, in which I chose the incorrect answer. The problem is, based on my understanding of kinematics I am unsure as to why I got it wrong.1. The question stated: Miley Cyrus (not kidding) suddenly falls out of a tree at the exact time that a projectile is fire upon her, the projectile hits her True or False?
2. Vy=Voy+a(t) and Vx=(Vo)cos(θ)
3. I chose False... I figured, since the projectile will be aimed at an angle anticipating her position BEFORE her sudden fall from the tree, that the projectile would pass through the area where she was before falling; furthermore, since time has passed, and Miley's acceleration is -g, then she would be lower than the projectiles trajectory. Imagine a sniper shoots at her from 1km away and it takes the projectile 1sec to reach her position. Since Miley suddenly fell, she would have moved -9.81m in the time it took the projectile to reach her former position; therefore they wouldn't collide.

Additional Info: In class the teacher said the projectile is not fired directly below her, that's all the info we got.
Teachers reasoning for the answer to be true: "Do you think I would miss Miley Cyrus."
 
Last edited:
Physics news on Phys.org
I am afraid this problem is ambiguous. What does "fired upon her" really mean?

We know that if a gun is aimed properly, it will hit a stationary target. If the target is then to move, the gun will obviously miss the target.

On the other hand, if we know in advance that the target moves while we shoot we can take that into account when we aim; that is how guns shoot at moving targets.

So, both situations are possible, but we need to know how exactly the shot was set up.
 
If the gun is aimed at her (or any other position), the bullet will not pass through that position because it follows a parabolic trajectory and not a straight line. The bullet has a downward displacement from the line of sight. The same displacement as the falling object (the one the gun was aimed at).
So the bullet hits the target. It's a nice experiment to do in the classroom. See this, for example.
http://www.youtube.com/watch?v=cxvsHNRXLjw
 
The complete argument runs like this: assume, as nasu says, that the person firing the projectile made no allowance for gravity and simply pointed straight at Miley. If it takes time t for the projectile to cover the horizontal distance to Miley, then it will be 0.5gt2 below where Miley had been (i.e. below where it would have been without gravity). In the same time, Miley has fallen 0.5gt2, so the projectile hits the target.
 

Similar threads

Replies
40
Views
3K
Replies
15
Views
3K
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 16 ·
Replies
16
Views
6K
Replies
14
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K