Grade 12 Physics problem -- A small bungee cord powered catapult

[PatrikL]

Homework Statement

I am really stuck on this problem and need help. Please see pictures.

Relevant Equations

Please see picture

 

[berkeman]

Welcome to PhysicsForums, Patrik.

It looks like you left some information out of your "Problem Statement" above. Could you please post the whole problem statement? The problem does not seem to have enough information to me.

Also, please post your work to start trying to figure out the solution. What you have posted as an image above seems more like some more details about the problem.

Thank you.

 

[PatrikL]

Hi.
That is all the information our teacher gave us...

 

[berkeman]

Hi.
That is all the information our teacher gave us...

That's very doubtful. What is the difference between the problem statement image that you posted and the image of your handwriting? Why did you need to post the additional image of your handwritten notes if the problem statement was complete?

The main issue I have is there is no information in the problem statement that has anything to do with friction or elastic energy losses...

 

[Lnewqban]

Welcome, Patrik!
Did you get the numbers that you have shown from a diagram?

 

[PatrikL]

Welcome, Patrik!
Did you get the numbers that you have shown from a diagram?

Yes they did

 

[haruspex]

Yes they did

So the information in your handwritten image is just part of the problem statement, and you have not posted any attempt. That violates forum rules.
It may still be helpful to see the diagram. It could contain information you have overlooked.

The first step is to find how much energy was stored in the stretched elastic. Please attempt that.

 

[PatrikL]

Hi here is my attempt. Not sure if it is correct but I'm trying .

 

[Herman Trivilino]

Hi here is my attempt. Not sure if it is correct but I'm trying .

You need to follow the prompt given to you in Post #7. First, find the amount of potential energy stored in the elastic bungee cord. (Note that in your Step 6 you have assumed it to be zero!)

 

[PatrikL]

Hi. I used the above suggestions and arrived at this ..see picture

 

[Herman Trivilino]

In Step 1 you are finding the initial speed. This was not the suggestion. The suggestion was to find the initial elastic potential energy. That should be Step 1.

By the way what makes you think the acceleration is a constant 9.8?

 

[haruspex]

Hi. I used the above suggestions and arrived at this ..see picture

If you had read the forum rules you would also know that images are for printed matter and diagrams. Your handwritten posts are too hard to read. Please take the trouble to type in your working. LaTeX is preferred, but you can also use the "..." pulldown above the typing area for subscript and superscript and $\sqrt x$ button for special characters.
Also, I strongly recommend working entirely symbolically until the final step. Resist plugging in numbers straight away. Create variable names for the given numbers. This has many advantages.