Is My Formula Rearrangement for Vertical Circle Travel Correct?

[RichMortimer]

Query over tutor help on question... Please help!

Homework Statement

I have a problem to solve regarding travel in vertical circles and know the required formulae. However, I'm being told that my rearrangement of the formulae is wrong!

Homework Equations

mv^2/r = mg and I need v.

The Attempt at a Solution

My solution to isolate v is:

v = √rg

However my tutor tells me it should be:

v = rg

I know this is simple stuff but I'm obviously missing something!

Please an someone shed some light on this please?

Thank you!

 

[SteamKing]

Time to find another tutor.

 

[gneill]

Ask your tutor to show you how the units work out in his version.

 

[RichMortimer]

So am I right with... v = √rg ??

Is there any other possible way that v = rg like he says?

 

[RichMortimer]

P.s. the problem is that it took me 3 weeks to get that from him! The submission date is 1!

 

[gneill]

So am I right with... v = √rg ??

Is there any other possible way that v = rg like he says?

Nope. However, it is possible that you misinterpreted what he gave you! If ω is the angular velocity, then v = rω.

 

[gneill]

Perhaps it would help if you were to post the actual problem statement so that we can see how your formula mv^2/r = mg arises. For example, are you looking for the minimum velocity at the top of a vertical circle for an object being slung around at the end of a string?

 

[RichMortimer]

Nope. However, it is possible that you misinterpreted what he gave you! If ω is the angular velocity, then v = rω.

Hi gneil,

The question to solve is:

Calculate the minimum speed for an object to travel in a vertical circle of 1.5M (Radius)

In my textbook an example of this question uses the formulae mv^2/r = mg

In order to solve this I need to calculate v, and here lies the previous problem.

My final answer to the problem is: 3.84ms-1

Any help is very very much appreciated!

Thanks.

 

[gneill]

Well, your result looks okay to me.