Friction

On Monday the force was equal to the change in momentum - much to my surprise and wonderment. Laboratory five was still able to build on the Wednesday exercise where I presented Newton's laws of motion using my RipStik and a four square ball as an on-sidewalk presentation.

During that presentation I noted that an object in motion will remain in motion unless acted on by an external force, and I then wrote off the tendency of the board to stop rolling to friction. This provides the segue into the investigation of friction.

At 8:00 I had the students try to work out what the variables might be. At 11:00 the variables were already on the board, so I left that material up. I closely followed the lab in the textbook including copying the following questions onto the board.
• What factors contribute to friction: weight, surface area, or surface roughness?
• Which factor contributes the most?
• Which factor contributes the least?
• What is the nature of the relationships between the factors and the force of friction
A data sheet was also provided to assist the students with gathering data.

The 8:00 class obtained data similar to that seen in the past.

One group in the 11:00 section obtained what appeared to be a logarithmic decay for surface area versus the kinetic force of friction.

As in prior terms, on Friday the students shared their functions. A couple pairs were minus the member with the data. The data I had picked up on Thursday proved useful to reporting functions in these instances. The functions proved useful in a wrap-up discussion of the results, the upshot of which is that friction is primarily dependent on weight. There might be a very small negative relationship to surface area, and grit appears to have no effect on friction for the glass - somewhat counter-intuitive as rougher surfaces feel more frictive.

Ashlyn works on surface area

Jesse

Swister and Masabua

Brenda and Junida

Chastity, Caslyn

Mayson

Gina, Emerika, Nemely

Ian, Harvey

Dexter, George

Lillian, Enerico

Kiokalani, Vivian