Find Optimum Angle of Launch: Calculate Velocity of Ball from Catapult

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The discussion focuses on calculating the velocity of a ball launched from a catapult at a height of 0.5m and an angle of 45°, with the ball landing 1.45m away. Initial calculations yielded a velocity of 37.6 m/s, which seemed implausible given the observed time of flight. The user clarified that they measured distances for multiple angles to determine the optimum launch angle, which is typically 45° in the absence of air resistance. A misunderstanding regarding units was identified, as the user initially used centimeters instead of meters, leading to incorrect calculations. The conversation emphasizes the importance of using the correct units and equations when analyzing projectile motion.
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Hello, i have to work out the velocity of a catapult which i had to do for my AS Quality of measurement coursework where I'm trying to find the optimum angle of launch.

Homework Statement



A ball is fired from a catapult 0.5m above the ground, the ball hits the ground 1.45m away, the angle of launch is 45°. Calculate the velocity of the ball.

Homework Equations


v^2= u^2 + 2as

The Attempt at a Solution



Attempted it by plugging numbers into that equation but comes up with 37.6 m/s, whilst watching the catapult fire it took a few seconds to land so it couldn't be that fast, although after using Time = Distance/Speed it appears to be 3.9s which could be right but I'm not sure. Am I using the wrong equation i need to compare this to other angles but not sure what equation to use with angles.
 
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Sorry, are you trying to find out the optimum angle of launch? Because you stated an angle in section one, the known data.
 
I was using 45° as an example, whilst doing the experiment I measured the distance traveled for 11 angles at 5° intervals from 20° to 70°. As 45° is the optimum angle excluding air resistance I'm going to work that one out first and compare to other angles. Should of included more detail. :smile:
 
How did you get the to answer of 3.9 seconds and 37.6 ms-1? From what you have given me in section one (the known data) I can only find the horizontal distance and the launch angle, and I cannot understand how you find your given answer from that. Is there a missing piece of data that you might have forgotten?
 
I worked it out for myself, noticed i was making a huge error by putting the displacement in cm instead of metres, silly me. :smile:
 

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