Lab 5-6C: Friction on an Incline

1. Lab 5-6C: Friction on an Incline

2. Lab Recap: Friction • µs > µk for the same 2 materials • µs and µk do not change on an incline • If constant velocity downward, Ff = F// = Wxif no other forces acting in motion direction • µs and µk unaffected by changes in surface area of contact

3. 1. How can you find μs easiest? • Tug horizontally with known amount of force. • Slowly increase force applied until object starts to slide • Maximum force applied = maximum friction that can be created. • μs = Ff / FN

4. 2. How else can you find μs? • Make plank into incline and set block on it. • Slowly raise incline until object starts to slide • Use angle of repose equation for static friction: μs = tan Θ

5. 3. What are two ways to… • Lower the μk value between block and incline? • Raise the μk value between block and incline?

6. Rolling friction • μr is usually much lower than μk for same two materials • Ffr does not increase with increased speed • 4. Describe how you would find the coefficient of rolling, static, and kinetic friction between tires and road for the red cart!

7. 5. What is the height that a block will rise if it is given a 1.5 m/s push up an inclined plane that has μk = 0.40 with the block if the angle of inclination is 60⁰?

8. Vertical Acceleration Problems Ch 6 Notes

9. Free Fall with Drag Forces • Acceleration in free fall is at its maximum when the falling object is at its slowest • As relative velocity increases, so does FD • V-t graph tends to horizontal as time wears on • Y-t graph becomes more and more linear as time wears on • a = 0 m/s2 when terminal speed is reached. • More in a few weeks….differential equation

10. Elevator Problems • There is always FG acting on an object in an elevator or the elevator itself • There is always a FT from a cable (or cables) holding the elevator up. • There sometimes are Ff forces restricting relative motion. • When constant velocity up or down, no net force in the y-direction