Calculating Trebuchet Velocity: A Homework Help Guide

• steve092
In summary, calculating trebuchet velocity requires understanding of the projectile's weight, distance from the pivot point, and the counterweight's mass and distance from the pivot point. The formula for calculating velocity is v = √(2gh), where v is the velocity, g is the acceleration due to gravity, and h is the height of the projectile at the point of release. To improve accuracy, it is important to account for air resistance and wind conditions. Additionally, using a simulation or physical experiment can help determine the optimal counterweight mass and release angle for achieving maximum velocity.
steve092
Trebuchet help: Calculating velocity

Homework Statement

I'm new to this site, so bear with me!
OK, so I'm doing a trebuchet for my physics project. I have done three trials with counterweights of different masses. I have all of the distances that a golf ball of mass=0.045kg has traveled. I also have the masses of the counterweights.
Just as a starting point for the first trial:
mass of the counterweight=10.937
h=0.631m

The average distance for this trial was 34.33m.

PEg=mgh
KE=(1/2)mv2

The Attempt at a Solution

I've done the calculations; however, my answers were nowhere near what the velocity should be. For one trial, the mass of the counterweight was 10.937kg. I did the calculations and the velocity came out to be 3.53m/s which seemed a little slow.

Obviously, I'm doing something wrong. I wonder if it is because the mass of the golf ball needs to be taken into account somehow? Anyways, thanks in advance!

I've used the example from https://www.physicsforums.com/showthread.php?t=250335&highlight=trebuchet and I still can't get it. I don't even understand how the answer was calculated in that example.

Last edited:
Well, I think I might have it! I used that example in the post I linked to in the previous post, and I just changed the values to fit my case. I did the other example to get the right answer that was provided. So, I'm assuming that my answer is correct

Here are the givens:
m1=10.937
m2=.045
h1=.076
h2=.838

I used:
m1gh1-m2gh2=(1/2)m1v12+(1/2)m2v22

And I used the proportion:
v1 .076
-- = --
v2 .838

And just solved for v2.

My final answer was 10.742 m/s which sounds correct, but I'd like to see if I made any mistakes.

That proportion I used, v1/v2= 0.076/0.838, what exactly is that?

OK, I think that solved for velocity correctly. Using the calculated velocity and the average distance traveled of the golf balls in a trial, I calculated a time of about 3.3 seconds. When I launched golf balls and manually timed it, the results were close enough.

1. How do I calculate the velocity of a trebuchet?

To calculate the velocity of a trebuchet, you will need to measure the length of the throwing arm, the mass of the projectile, and the angle at which the arm is released. Then, you can use the formula v = √(2gh) to calculate the velocity, where v is the velocity, g is the acceleration due to gravity (9.8 m/s²), and h is the height the projectile is released from.

2. What units should I use when calculating trebuchet velocity?

The units used for calculating trebuchet velocity will depend on the units used for the measurements of length, mass, and angle. For example, if length is measured in meters, mass in kilograms, and angle in degrees, the resulting velocity will be in meters per second (m/s).

3. How does the angle of release affect trebuchet velocity?

The angle at which the trebuchet arm is released can greatly affect the velocity of the projectile. As the angle increases, the height at which the projectile is released also increases, resulting in a greater overall velocity. However, if the angle is too steep, the projectile may not have enough time to gain sufficient velocity before hitting the ground.

4. Can I use the same formula to calculate velocity for different trebuchet designs?

The formula v = √(2gh) can be used for most trebuchet designs, as long as the basic principles of the trebuchet are the same. However, some designs may require slight modifications to the formula, such as taking into account the length of the sling or the weight of the counterweight.

5. Are there any other factors that can affect trebuchet velocity?

Yes, there are several other factors that can affect trebuchet velocity, such as air resistance, friction, and the elasticity of the trebuchet arm and sling. These factors may be difficult to account for in calculations, but can have a significant impact on the actual velocity of the projectile.

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