physics science fair project. Need help fastt!!!?

So tomorrow I have my science fair project presentation and my project is a roller coaster made out of materials I found in my house that were reliable to make an appropriate project. My "roller coaster" consisted of a 4 feet high starting point and a loop that was adjustable to any radius ranging from 5 inches to 6.5 inches. My question is "how does the radius of a circular loop affect the speed required for an object(marble) to complete the circular loop?" I tested 4 radius that were 6.5 in, 6 in, 5.5 in, and 5 in. I found the heights that each individual radius require the object to have in order to complete the loop but I'm still not sure how to conclude how the speed is affected by the radius of the loop. Can I get some helpp please!

My results were:

Radius 6.5 in = height of 1.8 ft

Radius 6 = height of 1.6 ft

Radius 5.5 = height of 1.4 ft

Radius 5 in = height if 1.25 ft

3 Answers

  • 7 years ago
    Favorite Answer

    this is an energy question

    the potential energy at the starting h is M*g*h

    the kinetic energy at the top of the loop is 1/2 *m*v^2

    the potential energy must be such that KE is greater than zero at the top of the loop, at least!

    the height drop from the starting point to the top of the loop is the only dependance in an ideal world, the radius does not matter. So as long as the starting point is just above the top of the loop, h>0, the rollercoaster will complete the loop. However, there's a big difference in yours, that's due to friction between the cart and track.

    In you equations:


    total energy = mgh



    total energy =1/2mv^2


    h is proportional to v^2, g and m are constant

    the 'extra h' is the frictional energy to be over come which is simply:


    where, h is the starting height above the top of the loop

    you can go into more detail if you want here:

    and there's a niceanimation of what I explained here:

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  • 7 years ago

    I don't know how you arrived at launch heights, but what you should do is for each radius of loop, reduce the height and repeat the launch until the marble comes free of the track at the top of the loop. Then increase the start height gently until the marble is able to complete the loop without unsticking at the top. That is the minimum launch height for each radius change.

    Your figures may well be right if you followed such a procedure, but if not, start again.

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  • 4 years ago

    All people is doing whatever on solar energy. I have an concept for you that may use physics and astronomy. Design an elevator that may go the entire means up into area ! Were you aware if an area shuttle lower back to earth and it used to be stuffed with gold it still wouldn't be enough money to pay for the shuttle ? It fees about $10,000 to position one pound into area. It has to arrive 17,500 MPH to go into orbit. But if we were to position a small asteroid in an earth orbit at 22,000 miles up and extend a cable to the earth and connect it to an ocean ship. You could use it as an elevator. So NASA is opening to have contests to make elevators. They put them on a 200 foot tall crane and shine spot lights on the

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