1. Static Friction: no surface motion.
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2. Friction is dependent on FN --- Not on contact area
Friction is dependent on FN --- Not on contact area
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3. Kinetic & Rolling Friction: surface motion
Sliding Block:
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5. A pickup truck accelerates smoothly and a box in back does not slide
A pickup truck accelerates smoothly and a box in back does not slide. Is there surface motion as defined?
Yes No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
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6. As defined, coefficients of friction are
Dependent on normal force.
Dependent on materials used.
Dependent on both the above. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
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7. Block at rest. Draw a Force Diagram for the block.
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8. Three boxes are pushed by force F with v > 0 along a horizontal surface with mk = 0.291.
F=26N
3kg
5kg
2kg fk
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9. Motion Along a Curved Path
Motion Along a Curved Path
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12. Assume the car has m = 1200kg and ms = 0.92.
Assume the car has m = 1200kg and ms = 0.92.
At what speed would the car begin to slide?
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13. Which force diagram applies to the object at Point D?

14. 5-4 Numerical Integration: Euler’s Method
Skip
5-4 Numerical Integration: Euler’s Method
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15. End
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16. Both have same centripetal acceleration
A disk rotates at a constant rate. Consider two points on the disk, one at radius R/2 and one at radius R. Which point has larger centripetal acceleration?
Point at R/2
Point at R
Both have same centripetal acceleration 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
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17. Is it possible for an object to have a non-zero acceleration when the velocity is constant?
Yes No
Cannot be determined 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
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18. Maximum angle block remains at rest:
Derive the Angle of Repose relation:
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19. Atwood with Friction:
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20. Can you stop in time?
Buggy rolls. You slide.
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21. Insert values, determine ax.
Given m = 75kg, M = 20kg, D = 3.5m, vo =1.1m/s. What frictional coefficient is needed?
Insert values, determine ax.
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22. Diagramming Refresher:
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23. Stopping with 4W Disc-Brakes
Accelerating with F2WD.
Stopping with 4W Disc-Brakes
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24. (60° is close to maximum angle)
A 3kg box at rest on level surface with ms = What is the largest F acting 60° below horizontal for which the box remains at rest? fs
(60° is close to maximum angle)
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25. Relative vs. Absolute Velocity
vpc
vpg P
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26. Which force diagram applies to the object at Point B?

27. Which force diagram applies to the object at Point C?

28. Assume mass = 1. 2kg and radius = 45cm. If speed at Point D is 3
Assume mass = 1.2kg and radius = 45cm. If speed at Point D is 3.6m/s, what is the size of the normal force acting at Point D?
-cen
+cen
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29. Q. Assume mass = 1. 2kg and radius = 45cm. If speed at Point B is 5
Q. Assume mass = 1.2kg and radius = 45cm. If speed at Point B is 5.1m/s, what is the size of the normal force acting at Point B?
+cen
-cen
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30. Given: T = 50N, q = 30°, r = 1m Find: mg and v.
Net
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31. The speed is now 6.5m/s and r = 1.0m. Angle, tension, mass?
Net
For example, if m = 1.0kg,
then T = 42.3N.
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32. Q. The speed of a mass on a string of length L is 6. 5m/s
Q. The speed of a mass on a string of length L is 6.5m/s. The radius r = 2.0m. Find angle, tension, mass, and L.
Net
For example, if m = 1.0kg,
then T = 23.9N.
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33. Practice Q: What is F such that 0
Practice Q: What is F such that 0.5kg block stays at rest if all surfaces are frictionless?
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34. Banked Turn:
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35. Banked Turn:
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36. Modified Atwood Machine with friction.
Objects are in CW motion.
Let m1 = 2kg, m2 = 3kg, q = 30°, sliding friction coeff. 0.44
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37. Q. Recalculate last problem with m1 = 6kg m2 = 1kg
Q. Recalculate last problem with m1 = 6kg m2 = 1kg. (All else remaining the same)
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38. Practice Q: Find the variable relationships.
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40. Figures
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55. Q. Assume the car has m = 1200kg and ms = 0.92.
Q. Assume the car has m = 1200kg and ms = 0.92.
How large is the frictional force if v = 15m/s?
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56. 5-3 Drag Forces
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57. Drag Forces Can be approximated as, Fdrag = bvn
Drag Forces
Can be approximated as,
Fdrag = bvn
where b and n are constants
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58. Example: Air drag, n = 2.
If b = 25N/(m/s)2, at what speed would the object be resisted by 10N?
At what speed would the same object be resisted by 30N?
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59. Drag force grows quickly with v:
Terminal Velocity:
Reached when drag force equals weight force
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