Investigating Friction - 16&17/11/11

Yesterday we investigated how our toy cars went down a ramp and how far they moved after leaving the bottom of the ramp. In particular we looked at three things:

  1. the height of the ramp - the lowest and 1st rung up (higher than that and the car was likely to go off the table!)
  2. different cars - it was fun to test whose car went the furthest
  3. the surface of the ramp - we had four different surfaces: underfelt, rubber, sandpaper and wood

We discovered that the smooth wood ramp let the car go the furthest, but we decided we would like to investigate FRICTION some more, so we did the investigation you see in the photos below.

We tied up some bricks and tested the force (measured in Newtons) it took when we pulled so that the brick just started to move on different surfaces. We checked which forcemeters were the most suitable to use for this activity and decided that the yellow and brown ones measured forces best in the range we were pulling at. Apart from having different surfaces to pull the brick over (the variable), we tried to keep everything else the same to make it a fair test.

On sand On newspaper On gravel On a metal tray On the carpet

On the sand we found that the brick tended to dig into the sand and we managed to spill lots of it onto the carpet, but we brushed up most of it later and the hover cleared the rest!

We found that the brick started to slide with a much smaller force on the smooth metal tray than it did on the other four surfaces. Clearly the smooth wood of the ramp and the smooth metal of the tray had much lower friction than the other surfaces (materials) we tested.

We concluded that the smoother the suface, the lower the friction, the easier it is to slide over it and the rougher the surface, the higher the friction, the harder it is to slide over it.

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