Join TSR now and get all your revision questions answeredSign up now

Whirling Bung Experiment - why does the weight move up?

    • Thread Starter
    Offline

    3
    ReputationRep:
    Now, I know that as the bung is swung in a horizontal circle, the suspended weight remains stationary as long as the force provided (Mg) is equal to the centripetal force required to make the bung travel in its circular path.

    However, my book later says

    If the centripetal force required is greater than the weight, then the weight moves upwards.

    I know this would increase the radius in the formula F = mv^2 / r
    but it does not make sense how this happens.

    Can someone explain why?

    I thought since a = v^2 / r, a greater v would mean a larger r is required, hence the weight moves up to give a greater radius from the string.

    Is that correct?
    Attached Images
     
    Offline

    3
    ReputationRep:
    (Original post by nwmyname)
    Now, I know that as the bung is swung in a horizontal circle, the suspended weight remains stationary as long as the force provided (Mg) is equal to the centripetal force required to make the bung travel in its circular path.

    However, my book later says

    If the centripetal force required is greater than the weight, then the weight moves upwards.

    I know this would increase the radius in the formula F = mv^2 / r
    but it does not make sense how this happens.

    Can someone explain why?

    I thought since a = v^2 / r, a greater v would mean a larger r is required, hence the weight moves up to give a greater radius from the string.

    Is that correct?
    well in this demo the force is a constant so if you increase v then r will increase (i.e. move the weight upwards) until you reach a new equilibrium position... btw this isn't like planets orbiting round the sun because the gravitational force varies as 1/r2
 
 
 
Write a reply… Reply
Submit reply
Updated: October 3, 2016
Poll
Which party will you be voting for in the General Election 2017?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.