# Friction and speed

Have you ever tried sliding on a wooden floor or an icy surface? It’s much easy to skid on a smooth surface like wood then a rough surface like carpet, this is because of friction. Friction is created when things are pulled past each other. The rougher the surface the more friction is created. Have you ever hurt your knee when sliding on carpet? This is because of the friction created between your skin and the carpet.

What happens if you try to slide with socks and then bare feet?

For this investigation we made our own friction ramp.

A ramp – we made this one using a sheet of plywood, gaffer tape and some carpet.

Cars – LEGO/DUPLO or K’Nex

Chalk

Tape measure

We are investigating the effect of friction on the distance travelled by a car, so the ramp surface is our variable, everything else must be kept constant.

Do not push the car, just let it go without any force behind it.

### Method

How does the surface of the ramp affect distance travelled?

Allow the car to roll down the smooth side of the ramp. Measure and record how far it travels.

Repeat using the carpet covered side of the ramp.

Gathering data

We repeated each test 3 times and found the average distance travelled by the cars and recorded in a table.

Results

Our cars travelled a shorter distance when we used the carpet surface than when we used the smooth surface. This is because there is more friction between the car and carpet than between the car and smooth surface. The frictional forces act in the opposite direction to movement making it harder to move, therefore making the car slower and pick up less speed moving down the ramp so travelling less distance.

Friction between our shoes and the floor stop us from slipping and sliding around.

Friction between tyres and the road stop cars from skidding, when the road surface is icy there is less friction which makes it more likely cars will skid.

Friction between brakes and wheels help bikes and cars slow down

Four younger children

Try pushing the car and comparing with the distance travelled if you don’t push. Does the extra force make a difference?

Suitable for Key Stage 2

Forces and Magnets

Compare how things move on different surfaces

Working Scientifically