- #1

colonel

- 9

- 0

Also, say the distance between the chords are increased, the holder is pulled back and down (3-D)how will I measure the "x" value for the equation E= 1/2 kx^2?

Thank-you for your time.

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- Thread starter colonel
- Start date

- #1

colonel

- 9

- 0

Also, say the distance between the chords are increased, the holder is pulled back and down (3-D)how will I measure the "x" value for the equation E= 1/2 kx^2?

Thank-you for your time.

- #2

arcnets

- 508

- 0

I'm afraid I don't quite understand the problem. Are the chords meant to be vertical in the original position? Is 10 cm the diameter of the softball holder?

- #3

colonel

- 9

- 0

There is a plastic funnel for the softball. Attached to the funnel are two surgical chords, about 1 m in length each. The funnel and the two chords form the "slingshot". To measure the spring constant, I hung the "slingshot" from a bracket on the wall. In this position, the two chords were 10 cm apart (same width as bracket). To launch the softball, there are two people holding onto the chords, one person per chord. But you cannot have the two people standing 10 cm apart as they will get whacked when the softball is released. The two people spread apart a little, say both go 1 m. The third person pulls the funnel (with the softball) back and down, and releases it. As you can see, there are 3 dimensions here : each chord goes 1 m away from an imaginary centre, back 1m from the pull, and down 1 m from the pull. Does this change the spring constant and how would I determine the "x" value for the equation E = 1/2 kx^2? Once again, thank-you for your time.

- #4

gnome

- 1,037

- 1

But that is very different from the forces involved in your final "apparatus". There, each piece of cord [not chord :)] exerts a force on the cup based on the spring constant of the tubing,

There's another problem. Your "spring" is not just the rubber tubing. Your "spring" includes the two people holding the ends of the cord, and the tension in their muscles will definitely play a very significant role in the propulsion of the ball. When the third person releases it, those two people will suddenly jerk in the direction of flight; it's almost inconceivable that they will be able to avoid doing so. Therefore, their muscles will also be contributing to the force that launches the ball. Your experiment would be more accurate if you could replace them by two poles anchored securely in the ground & simply tie the cord to the poles.

Either way, you should re-measure your spring constant with your apparatus configured exactly the way it will be set up for the actual trial. For example, have the "puller" use a spring balance to pull the funnel back several measured distances & record the amount of force needed in each case. If you do this for several different stretch distances you may be able to determine if there exists a linear (or approximately linear) relationship.

By the way, if all you are really trying to do is determine the potential energy of the system, there is a much easier, and probably much more accurate way, that doesn't involve that formula U = (1/2)kx

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