Measuring Friction?

Question

I carried out an experiment to find the friction of different materials.

I have an angled surface. I rolled a pingpong ball down the surface and recorded specifically how long it took to reach the bottom. The material that friction I wanted to measure was placed on top of that surface.

My aim of the experiment was: To measure the friction of different materials
So with this data, how would i produce my results. Be very specific, as I'm not the greatest scientific mind.

Answer 1

Note on this experiment you will be measuring rolling friction.

The acceleration of the ball will be determined by the forces acting on it in the direction of the angled surface. If the angle of the surface with respect to horizontal is ø, then the force pulling the ball down is m*g*sinø. The acceleration is a = F/m = g*sinø.

When friction force Fr is added, the net force is F = m*g*sinø - Fr and the resulting acceleration is a = g*sinø - Fr/m. If the time it takes for the ball to roll down the plane is t then its acceleration is t^2 / 2*L, where L is the length of the plane. So this is your process:

Measure the time it takes for the ball to traverse the plane with each different material; find a from the above formula. Then find Fr from a = g*sinø - Fr/m. I assume you can weigh the ball to get m.

Answer 2

It is nice to see someone still coming up with their own experiments.

There is only one error in you data collection. The ping pong ball cannot roll. When the ball rolls their is no "rubbing". Look at a car wheel for instance, the tread is stationary with the ground even as it moves. This is an easy fix, just trade the ball for something square or if you really need the surface of the ping pong ball, glue three or four together.

The angle of the slope is equally as important as the time in you calculations.


I could give you a plug and chug answer but that wouldn't be any fun.

Here are some helpful sites
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
http://www.engin.brown.edu/courses/en3/Notes/Statics/friction/friction.htm

When you get some answers compare them to published values
http://www.school-for-champions.com/science/frictioncoeff.htm

Goodluck!