## May the Force be with You

Today's lesson was about Force and Friction.  What are they?

Force is a push or a pull on an object

Friction is the force between two surfaces that are trying to slide across each other.  Friction always slows down a moving object.   The amount of friction depends on the material the two objects are made of. The rougher the surface the more friction there is.  For example, two pieces of silk easily slide across each other whereas trying to slide two pieces of Velcro across each other would be much more difficult.

Super-Duper quick experiments to show Friction in action

1) Rub your hands together nice and fast.  What do you feel?

Your hands get warmer.  That is because friction produces heat.

Put a blob of hand cream or oil on your hands and rub together for a few seconds.  Did your hand heat up?  The cream should have reduced the friction between your two hands and little or no heat should have been produced.  This is why oil is added to engines, so the moving parts that rub against each other don't overheat.

2) Take off your shoes and see if you can slide on a smooth surface, like a tiled or wooden floor.  (Be careful not to slip!)  Now put you shoes on or go barefoot and see if you can slide.

What is the difference? Why did this happen?

Because of Friction!  The grips on your shoes and the skin on your feet cause friction between them and the floor which slow you down.  If you had water or oil on the floor, that could reduce the friction and you could slip (don't try that one!).

Can you slide in you socks across a carpet? Why?

Friction! Trying to slide in socks is impossible on a carpet, there is too much friction between the two surfaces to be able to.

## Ray's Ramps

What you need to make your ramp:

To prop it up – books

For the ramp – Kitchen rolls cut in half-length ways. Or you can use a sturdy piece of cardboard or a large book.

You'll need a toy car or something that you can release (don’t push) down the ramp. And a measuring tape to see how far the car travelled.

Method:

Build you first ramp and prop it up with only one or two books.  Release your car down the ramp and then measure how far it went.  For you second test add another book or two to change the angle of the ramp and make it steeper.  Release the car again and measure the distance travelled.  Repeat a third time with an even steeper ramp.

 Test Number Number of Books Distance the Car Travelled 1 2 3

Now it time to add a bit more friction to our tests.  Keep the angle of the ramp the same for each of your 3 tests but change the surface the car will land on when it comes off the ramp.  Use surfaces less smooth that the surface you were using e.g carpet, rug, blanket, towel, sand, grass, gravel or whatever you can think of.

 Test Number Surface Distance the Car Travelled 1 2 3

Let us know how you got on with your all your experimenting.