Circular motion in horizontal plane VCAA 2012 exam 1

[joey7]

Hey guys Motion question 7 from vcaa 2012 has me a bit confused

It has a ball being swung in a horizontal circle and tells you that the breaking force of the string is 4.0N why then do you use the centripetal force and not the tension force in the string when calculating your answer?

[Alwin]

Hey guys Motion question 7 from vcaa 2012 has me a bit confused

It has a ball being swung in a vertical circle and tells you that the breaking force of the string is 4.0N why then do you use the centripetal force and not the tension force in the string when calculating your answer?

Oh this q

You do use the tension force, you substitute it in:
At greatest speed, centripetal force = maz tension = 4.0N

Cool beans?

EDIT: Also, i just double checked and the question is in the horizontal plane, for you to solve in this manner. Might want to fix up that subject line

[joey7]

Oh wow no wonder I couldn't understand why they had used only the centripetal force, so to clarify if it had have been in a vertical plane, then you would have to add the force due to gravity to the centripetal force to find the tension force in the rope??

[Alwin]

Oh wow no wonder I couldn't understand why they had used only the centripetal force, so to clarify if it had have been in a vertical plane, then you would have to add the force due to gravity to the centripetal force to find the tension force in the rope??

Yup, spot on

[kaiipoo_]

Remember that Centripetal Force isnt exactly a force in its own entity. It's a broad term that refers to whatever keeps an object in circular motion.

As Alwin said, in this situation, it is tension and that is why they can be equated.