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Post Number: 168
Posted on Saturday, 09 June, 2012 - 01:13 am:   

Hi Can anyone help with this question? It will be highly appreciated. An object of mass 6kg is whirled round in a vertical circle of radius 2m with the speed of 8m/s. If the string breaks when the tension in it exceeds 360N, calculate the maximum speed of rotation and state where the object will be when the string breaks.

I am utilising F = mv^2/r.

Maximum speed of rotation will supposedly act at Maximum tension.

T-mg = mv^2/r

Therefore, maximum speed is 10m/s at the bottom of the circle.
Veteran poster

Post Number: 596
Posted on Saturday, 09 June, 2012 - 03:36 pm:   

I haven't done this for some time.

I think for object whirled in a vertical circle the force is not constant. Identify all forces on the object and draw the direction of the forces when the object is at bottom of circle, at the top, line is horizontal and some general position. Why is this a problem for a "standard" force approach?

I think you need to consider energy (I have just checked Bostock and Chandler and that's their approach).

Post Number: 11
Posted on Sunday, 10 June, 2012 - 10:22 pm:   

You haven't asked a question here really.
Is the speed 8 or are we supposed to find the speed?
Frequent poster

Post Number: 170
Posted on Tuesday, 12 June, 2012 - 01:23 am:   

I wanted ro confirm if I was along the right path. Thanks for your assistance.

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