- #1
Calculating Initial Velocity for Symmetric Projectile Motion
- Thread starter doc2142
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Homework Help Overview
The discussion revolves around calculating the initial velocity for a projectile in symmetric motion, specifically in the context of a potato being launched through a wall opening and clearing a screen. Participants are exploring the kinematic equations relevant to projectile motion and the assumptions regarding the height at which the projectile clears the screen.
Discussion Character
- Exploratory, Conceptual clarification, Assumption checking
Approaches and Questions Raised
- Participants are attempting to identify useful kinematic equations and questioning the implications of the projectile's height as it passes over the screen. There is discussion about the concept of "reverse" projectile motion and its relevance to determining the necessary velocity components for the launch.
Discussion Status
The conversation is ongoing, with participants providing hints and suggestions for simplifying the problem. Some have offered guidance on considering the symmetry of the projectile's motion and the potential to adjust the height for easier calculations. There is no explicit consensus yet, but productive avenues are being explored.
Contextual Notes
Participants note the ambiguity regarding the height of the potato as it passes the screen and discuss the implications of this assumption on their calculations. The problem setup allows for certain simplifications, which are being considered in the discussion.
- #2
gneill
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Start by listing kinematic equations that might be useful. What's the maximum height of a launched projectile? How much time does it take to reach its maximum height?
The problem doesn't explicitly say what height the potato may have when it passes over the screen, so I suppose that you could assume that it just clears it at the screen's height.
Hint: can you find the equation for the trajectory of a "reverse" potato launched from the center of the wall opening and just clearing the screen?
The problem doesn't explicitly say what height the potato may have when it passes over the screen, so I suppose that you could assume that it just clears it at the screen's height.
Hint: can you find the equation for the trajectory of a "reverse" potato launched from the center of the wall opening and just clearing the screen?
- #3
doc2142
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I am a bit confused about your hint. a reverse? what is that exactly mean like wouldn't it need a velocity to go from the hole in the wall to the top of the screen?
- #4
gneill
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doc2142 said:
Yup. One property of projectile motion is that its trajectories are "reversible". You can launch a projectile and plot its trajectory to its landing point, and if you note its landing angle and speed, you can launch it from there back along its trajectory by using the same speed and angle to do so.
So what velocity (x and y components) would take a potato from the center of the window to the top of the screen as the trajectory apex?
- #5
JHamm
- 391
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Could you simplify this somewhat by removing 10cm of height from everything, setting your axis inline with where the projectile begins? Then perhaps consider the system as symmetric about the screen?
- #6
gneill
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JHamm said:
Yes! Those are two easy simplifications that hardly require any elbow grease to carry out
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