You are Here: Home >< Physics

# What causes an object to topple?

Announcements Posted on
Last day to win £100 of Amazon vouchers - don't miss out! Take our quick survey to enter 24-10-2016
1. I know an object topples when the line of action of the weight of the object is outside the base of the object, but i dont understand the other point to do with stability which is moment what do you comment on in the exam about the moment?
2. Moment is a turning force. It may cause something to topple. When you calculate moments of an object at rest on a surface, you are free to choose the point of rotation, although only two such points are interesting: the bottom left and right corners of the object in the table, since these will be the axes of rotation if the object topples anticlockwise or clockwise (respectively). So you want to calculate the moments about these two points. In general, there will be two moments about this point: the first due to the object's weight, which acts downwards at the COM, and the second is the reaction of the surface on the object, which acts upwards at the point directly below the COM where the object touches the table (assuming a flat bottom).

If you think about how these moments are calculated, depending on where the COM is relative to the two axes, it should become clear why the object will not topple (and is stable) if the COM lies between the two axes. A diagram of some random object (e.g. a square) may help make this clearer.

Just work out the moments of each of those two forces, as a function of the dimensions of the block (trig needed).

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: October 4, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

### Who would you like to thank?

Poll
Study resources

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

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