1. Force and Motion Physics 2053 Lecture Notes
Laws of Motion (Chapter 4) 2053.ppt

2. Forces Types Range Size 100 Gravitational Unlimited 106 1020
1035
Gravitational Unlimited
Electromagnetic Unlimited
Weak Nuclear  m
Strong Nuclear  m
Laws of Motion (Chapter 4) 2053.ppt

3. If no external force acts, an object maintains a constant velocity.
Newton’s First Law (Law of Inertia)
If no external force acts,
an object maintains a constant velocity.
Laws of Motion (Chapter 4) 2053.ppt

4. Mass Gravitational mass mg Inertial mass mi mg = mi
Laws of Motion (Chapter 4) 2053.ppt

5. Newton’s Second Law Units of Force System Mass Acceleration Force
SI kg m/s N = kg m/s2
British slug ft/s lb = slug ft/s2
Laws of Motion (Chapter 4) 2053.ppt

6. m Force of Gravity and Weight Weight = mg
Laws of Motion (Chapter 4) 2053.ppt

7. Action/Reaction Forces
Force block exerts
downward on table top
Newton’s Third Law F1
Force table exerts
upward on block F2
Action/Reaction Forces
Laws of Motion (Chapter 4) 2053.ppt

8. Applications of Newton’s Laws
Find Tensions T1 and T2 q
T1 sin(60)
T1 cos(60) T1 T2 mg m
q = 60o
m = 20 kg
Laws of Motion (Chapter 4) 2053.ppt

9. Applications of Newton’s Laws Another method qmg T1 T2 T2 mg m
Laws of Motion (Chapter 4) 2053.ppt

10. Applications of Newton’s Laws
vo= 0
Dt = 5 s
m = 5 kg F
v = ? m
Find velocity of
block after Dt
Laws of Motion (Chapter 4) 2053.ppt

11. Applications of Newton’s Laws
vo= 20 m/s
m = 5 kg
v = 0 F m d
Find distance
block moves
Laws of Motion (Chapter 4) 2053.ppt

12. Forces on m1 N T m1 T m1g m2 m2g Forces on m2
Laws of Motion (Chapter 4) 2053.ppt

13. Mass 1
Mass 2 T T m2
m2g m1
m1g
Laws of Motion (Chapter 4) 2053.ppt

14. y x q mg Frictionless incline N mg sin(q) mg cos(q) q
Laws of Motion (Chapter 4) 2053.ppt

15. m1 T T m2 m2g sin(q2) m1g sin(q1) m2g m1g q1 q2
Laws of Motion (Chapter 4) 2053.ppt

16. Friction: m mg Force of Static Friction N F fs
Laws of Motion (Chapter 4) 2053.ppt

17. Friction: v Force of Kinetic Friction N F fk m mg
Laws of Motion (Chapter 4) 2053.ppt

18. Table 5.2 Coefficients Of Friction Steel on steel 0.74 0.57
Aluminum on steel
Copper on steel
Rubber on concrete
Wood on wood
Glass on glass
Waxed wood on wet snow
Waxed wood on dry snow
Metal on metal (lubricated)
Ice on ice
Teflon on Teflon
Laws of Motion (Chapter 4) 2053.ppt

19. y N fk q x q mg a mg sin(q) mg cos(q) Acceleration on a rough incline
Laws of Motion (Chapter 4) 2053.ppt

20. Rough surface N T fk
m1g T
m2g
Laws of Motion (Chapter 4) 2053.ppt

21. F m 2m 3m Three mass system - find acceleration
Find the tensions in the string.
First find the acceleration of the system.
Laws of Motion (Chapter 4) 2053.ppt

22. T2 F m 2m 3m Three mass system - find T2
Laws of Motion (Chapter 4) 2053.ppt

23. T1 T2 F m 2m 3m Three mass system - find T1
Laws of Motion (Chapter 4) 2053.ppt

24. x y N q F N f mk F q f m mg mg Pulling a block
Pulling a block with constant speed x y N q F N f mk F q f m mg mg
The normal force
A man drags a 20 kg crate at constant speed across a floor by pulling on a rope inclined at 35 degrees above the horizontal. The tension in the rope is 40 N.
Find the magnitude of the
a) normal force exerted on the crate by the floor.
b) frictional force acting on the crate.
c) coefficient of kinetic friction between the crate and floor.
Laws of Motion (Chapter 4) 2053.ppt

25. y N F N mk F q f q m f x mg mg Pulling a block with constant speed
The frictional force
A man drags a 20 kg crate at constant speed across a floor by pulling on a rope inclined at 35 degrees above the horizontal. The tension in the rope is 40 N.
Find the magnitude of the
a) normal force exerted on the crate by the floor.
b) frictional force acting on the crate.
c) coefficient of kinetic friction between the crate and floor.
Laws of Motion (Chapter 4) 2053.ppt

26. N y F N mk F q f q m f x mg mg Pulling a block with constant speed
The coefficient of friction
A man drags a 20 kg crate at constant speed across a floor by pulling on a rope inclined at 35 degrees above the horizontal. The tension in the rope is 40 N.
Find the magnitude of the
a) normal force exerted on the crate by the floor.
b) frictional force acting on the crate.
c) coefficient of kinetic friction between the crate and floor.
Laws of Motion (Chapter 4) 2053.ppt

27. m = 200 kg vo= 20 m/s ms = 0.500 Truck’s maximum deceleration
Crate on truck
ms = 0.500
Truck’s maximum
deceleration
A flatbed truck traveling at 20 m/s is carrying a 200 kg crate of heavy machinery. The coefficient of static friction between the crate and the bed of the truck is The driver applies the brakes and brings the truck to rest as quickly as possible without the crate sliding
Find the
a) magnitude of the trucks acceleration when coming to a stop?
b) time of the acceleration?
c) distance traveled during the acceleration?
Laws of Motion (Chapter 4) 2053.ppt

28. A block is released from rest at the top of an incline.
Frictionless
A block is released from rest
at the top of an incline.
Find the final speed and the
time to side to the bottom. N d q mg
mg sinq
mg cosq q
Laws of Motion (Chapter 4) 2053.ppt

29. A block is released from rest at the top of an incline.
With friction
f = mkN = mkmg cosq
A block is released from rest
at the top of an incline.
Find the final speed and the
time to side to the bottom. N f d q mg
mg sinq
mg cosq q
Laws of Motion (Chapter 4) 2053.ppt

30. Force and
Motion
END
Laws of Motion (Chapter 4) 2053.ppt