Friction D. Crowley, 2008

Friction To understand how friction affects movement Sunday, August 09, 2015

Frictional Forces Look at the bike – what frictional forces can act on this bike? Draw out the bike in your book, and label all frictional forces you can think of One more? Probably the most important… tyre and road brake pad and rim wheel bearing pedal bearing links in chain air resistance or “drag”

Friction What is friction? How is it useful? How does it hinder us? Friction always tries to slow moving objects down – it opposes motion Friction is created whenever two touching objects or surfaces move past each other, as well as when objects move through air (known as air resistance or drag) Your task is to plan an experiment to investigate how frictional forces can affect movement – think about what you need to change, and what you will have to keep the same to make this fair and accurate

Friction Experiment Look at the friction plan – this is what you will be following when carrying out your experiment However, there are some deliberate mistakes! Read through the plan, and change the mistakes

Friction Experiment

Experiment Set up a stool with a rubber band around it, which can launch the margarine tub Place the tub on the first surface, marking where it is, and pull the elastic band back using the force meter to a known force Let the elastic band go, and measure how far the tub has travelled from the start mark to where it finished using a ruler Record your results, and repeat this 3x Then repeat the experiment as above, using different surfaces Start point End point Force (N) Surface 1

Results Surface No. & Description Distance traveled by tub (cm) Measurement 1Measurement 2Measurement 3Average Surface 1 Surface 2 Surface 3 Surface 4 Surface 5 Start point End point Force (N) Surface 1

Analysis Look at your results and analysis your findings: - –Which surface allowed the margarine tub to travel the furthest –Which surface allows the margarine tub to travel the least –What does this suggest about the frictional forces for each surface? –Can you explain how the energy has been transferred from the tub – what has happened to our kinetic (movement) energy?

Analysis In our experiment air resistance (drag) should have been the same, as we used the same margarine tub, but surface friction changed dramatically Friction is created whenever two touching objects or surfaces move past each other – the tub travels the least on the rough surface as this has more frictional forces, slowing our tub down so it traveled less distance The energy has been transferred from kinetic (movement) energy to heat (and possibly sound) energy as the tub travels across the surface

Force Look at the force diagrams – which way will the block move, and with what resultant force?