Need help with a confounding projectile motion problem.

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Homework Help Overview

The problem involves projectile motion, specifically calculating the initial velocity of a cannonball fired at a 45-degree angle that lands 100 meters away. The original poster expresses difficulty in solving the problem due to multiple variables and insufficient equations.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the use of kinematic equations and the need for two equations to address horizontal and vertical displacements. There are mentions of the relationship between the horizontal and vertical components of velocity due to the launch angle.

Discussion Status

Some participants have provided guidance on the equations needed to approach the problem, while others have raised questions about assumptions, such as the neglect of air resistance. The discussion appears to be productive, with hints at potential solutions being explored.

Contextual Notes

There is a question regarding the assumption of neglecting air resistance, which may impact the calculations and results. The original poster has not provided specific calculations, which may limit the depth of the discussion.

MisterNi
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Ok, here's the problem:

A cannon angled at 45 degrees above the horizontal is fired. The cannonball lands 100 meters away. What is the initial velocity?

I've tried using the kinematic equations, but I always end up with at least 2 variables with 1 equation. I'm just completely stumped. Any help to nudge me in the right direction would be greatly appreciated. Thank you.
 
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Post your calculations so that we can show you the solution/errors.
 
You have two equations: one to solve for the horizontal displacement and one to solve for the vertical displacement.
 
You certainly should have two equations- one for the horizontal position and one for the vertical position. Your two variables will be the horizontal component of initial velocity (which is equal to the vertical component because the angle is 45 degrees) and time.
 
May use the formula for horizontal range of a projectile

R = u^2sin(2theeta)/g
 
I'd say that your army is in trouble if you can only shoot 100 metres.
Actually, I just wanted to clarify if this is neglecting air resistance. That makes a big difference.
 
Thanks for BobG, HallsofIvy and mukundpa, I think I got the answer.
 

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