Physical Science 1 Lab: Friction

[@martinfoster5163]

Great video. I've used a digital scale to drag objects before. You can get a real time readout of the break free force (static friction) then watch the scale to get an average while dragging the sample on a surface. The calculation is simply divide the mass by the pulling force. I think that works. I used this method in the field to test motorcycle clothing samples on different road surfaces. However, I also like your method but it doesn't work so well in the field. I can use your method to test the friction of different fabrics/leathers on sandpaper grades which I use to test abrasion.

[@markmontgomery99]

Martin, my physics students do use a digital scale in order to measure both the static friction (break free as you said) and kinetic friction forces (dragging). Interesting to hear the real-world application of motorcycle clothing versus road surfaces.

[@martinfoster5163]

Thanks for replying. The friction of materials in motorcycle PPE is really important. Low friction for impact to avoid tumbling and high friction for sliding to enable braking.

[@tesla7774]

Good job brother keep going

[@Cevher7382]

Why did you drop the block on surface to calculate the kinetic friction?

[@markmontgomery99]

The block needs to be moving for kinetic friction to affect it. The kinetic friction is will stop the block from sliding if it is greater than the downhill force of gravity. The ideal situation would be to find the angle that allows the block to slide down the ramp with a constant velocity (no acceleration at all). Then the kinetic friction would be equal to the downhill force of gravity. coefficeint * m * g * cosine theta = m * g * sin theta It's hard to judge when that happens just by watching it and it's beyond the scope of my physical science class to discuss trigonometry and measure acceleration on an incline. My goal is for students to see that static friction is typically greater than kinetic friction. Thanks for watching!

[@KatlegoSebanyoni]

when we calculate average are we only adding angles or we should also add the heights?

[@markmontgomery99]

Only the angles. The height would depend on both the length of the board and the angle. Since you can place the block anywhere along the board and get the same results, the height doesn't matter.