With what minimal horizontal velocity can you throw a stone

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Homework Help Overview

The problem involves determining the minimal horizontal velocity required to throw a stone from a height of 20m at position A to clear a height of 10m at position B, with a horizontal distance of 40m between the two positions.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the velocity by adjusting the distance to 41m and applying basic velocity equations, but expresses uncertainty about the correctness of their result. Other participants question the clarity of the original question and request more details about the calculations.

Discussion Status

Some participants have provided feedback on the calculations, suggesting that the distance used in the calculations may be arbitrary and emphasizing the importance of using the given distance of 40m. There is an ongoing exploration of the assumptions made in the problem setup.

Contextual Notes

Participants note that the size and shape of the stone are unknown, which affects the clearance needed to ensure it successfully flies over position B. The discussion reflects on the idealized nature of the problem and the implications of modeling it mathematically.

goku12
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Homework Statement


With what minimal horizontal velocity can you throw a stone from position A so it it manages to fly over position B.

the distance between A and B is 40m
the height of position A is 20m
the height of position B is 10m

Homework Equations

[/B]


The Attempt at a Solution


I have tried to solve it by making the distance 41m getting the time then solved basic velocity equation and got 28.67m/s, but that probably isn't correct
 
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Hello goku, :welcome:

What is your question ?
 
Pls give is the exact question as or would be easier.. Consider reading guidelines for other information
 
goku12 said:
I have tried to solve it by making the distance 41m getting the time then solved basic velocity equation and got 28.67m/s, but that probably isn't correct
Yes, probably not correct. Can you please show the details of the calculations that you attempted?
 
gneill said:
Yes, probably not correct. Can you please show the details of the calculations that you attempted?
not much but here
76kQ_G.jpg
 
Your working looks fine to me.
The issue is in taking the horizontal distance as 41m. This is arbitrary. Since you don't know the size or shape of the stone you can't know how much clearance to give. You just have to work with the given 40m and say that it has to go further than that. Maybe only by 1mm or maybe even less. So using 40m gives you a speed which you must exceed. That's all you can say.

It's a bit of a mathematical game: you make a "model" - an idealised situation where you ignore some inconvenient or unknown details. Positions and objects become "points" with no size. Here the stone would hit B at 28m/s, but miss at any greater speed.
 

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