Lab 5-6C: Friction on an Incline

Lab Recap: Friction µ s > µ k for the same 2 materials µ s and µ k do not change on an incline If constant velocity downward, F f = F // = W x if no other forces acting in motion direction µ s and µ k unaffected by changes in surface area of contact

1. How can you find μ s 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. μ s = F f / F N

2. How else can you find μ s ? 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: μ s = tan Θ

3. What are two ways to… (a)Lower the μ k value between block and incline? (b)Raise the μ k value between block and incline?

Rolling friction μ r is usually much lower than μ k for same two materials Ff r 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!

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 μ k = 0.40 with the block if the angle of inclination is 60⁰?

Vertical Acceleration Problems Ch 6 Notes

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 F D 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/s 2 when terminal speed is reached. More in a few weeks….differential equation

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