Science homework - I'm puzzled. Is there a teacher in the house?

[seeker]

DD had to do a chart of the different forces needed in different activities - taking a pen top off - pulling, putting it back on - pushing and so on. Under rubbing out a word written in pencil, dd wrote "pressure" and was told that pressure wasn't a force. I would have thought it was - but whaty do I know, I'm a ~ English graduate!Can somebody put me out of my misery, please? I hate not understanding stuff 11 year olds know!

I'm not a science teacher, but I would have thought that presure is how hard you push and pull something.

Pressure is a measure of the force used - not a force in itself.

Rubbing out would probably be push and pull - push away from you, pull towards you, in rapid succession

ask martianbishop tonight - she's a fountain of knowledge for this sort of stuff

What about atmospheric pressure?

quick google tells me pushing and pulling are the inly 'forces' in gthis context - so agree with soapy that rubbing out is prob both

But you can't rub our without downward pressure - so how would you say that?

The downward pressure in pushing, isn't it? Pushing it onto the paper and then pulling it back.

Can't wait to hear the proper explanation from MB later!

Downward pressure is push too, I'd have thought.
Rubbing out involves friction - not sure if that's actually a force, but it gets taught with forces at our junior school.

I would say rubbing out requires push and pull forces.

One of the things I'm enjoying about being a secondary school parent - the homework's interesting!

also friction is a force that opposes the action of rubbing out

Scientifically, "pressure" is "force per unit area" so it's not the same as a force. In normal speech it is, of course - "Just apply a bit more pressure" - but the school is probably going to want to stress the pressure/force difference and so will want the words used in the scientific way.

Mind you, speaking as a former contact stress analyst, the thing that matters when rubbing out with an eraser is definitely the pressure applied... you have to push a big rubber harder.

Thanks all - still don't quite understand but dd says she does, so that's OK!

Pressure is a force exerted on a specific area. It is generally a push force. In the case of air pressure, it is the force of every individual gas particle crashing into the walls of its container. Pressure caused by shoes, for example, is the force of gravity on a body spread over the area of contact.