Warm Up The coefficient of static friction between a duck and some grass is 0.2. The weight of the duck is 30 N. 1) What is the maximum force of static friction on the duck? 2) What is the minimum force necessary to push the duck so that it slides? 3) If the force in part 2 continues to be applied will the duck’s speed increase, decrease or remain constant?

Inclined Planes (With Friction) Sum of forces in y direction = F N - F gy = ma  (should =0) Sum of forces in x direction = F gx – F f = ma x  (this will give acceleration down the ramp)

Example A 10 kg block sits on an incline plane. The coefficient of static friction between the block and the ramp is 0.4. If the ramp is tilted at an angle of 35 degrees will the block slide down the ramp? Justify your answer.

Practice A 10 kg block sits on an incline plane. The coefficient of kinetic friction between the block and the ramp is 0.1. If the ramp is tilted at an angle of 35 degrees what acceleration will the block have as it slides down the ramp? Justify your answer.  Find F fr  Find F gx

Lab Friction on inclines

Homework Worksheet