3 equilibrium of concurrent forces and

1. EQUILIBRIUM OF CONCURRENT FORCES

2. To analyze the forces at a point using the first condition of equilibrium. To apply the concept of friction to the first condition of equilibrium Objectives

3. a vector quantity an interaction between two objects or between an object and its environment changes the dimension or shape and/or motion of the object (translational or rotational) Force (F)

4. Metric System MKS kg m/s 2 or N CGS g cm/s 2 or dynes * 1N = 1X10 5 dynes English System FPS slug ft/s 2 or pound Units of Force

5. Contact Forces acts on the interacting objects which are physically connected with each other ex. Friction, Tension, Compression, Normal Force, Air Resistance , Applied Force, Spring Force   Two Categories of Forces

6. Applied Force ( F app )is the force applied to an object by another object Normal Force( N f ) is the support force exerted upon an object in contact with another stable object

7. Friction ( F k or F s ) is the force exerted by a surface as an object moves across it Air Resistance(F air ) is a special type of friction that acts upon object as it travel through the air

8. Tension(T) is the force that is transmitted through a string, rope, cable, or wire when it is pulled tight from both ends Compression (C) is an inward force on an object

9. Spring Force ( F spring ) is the force exerted by a compressed or stretched spring upon any object that is attached to it

10. Non- contact Forces acts on the physically separated objects ex. gravitational force , electric force, magnetic force

11. Gravitational force, Force of gravity, Gravity Force, Gravity, Weight is the force with which the earth, moon, or other massively large object attracts another object towards itself F grav or W

12. Magnetic Force is the attractive or repulsive force exerted on a magnetic pole Electrostatic force is the force between 2 charges at rest

13. Mass is the amount of matter of the object Weight is the pull of the earth (or any other planet) upon the object; dependent upon the value of g

14. W = mg where m is the mass of object g is acceleration due to gravity g = 9.8 m/s 2 = 980 cm/s 2 = 32 ft/s 2

15. *If forces(contact or non-contact) act on a common point of an object, these are concurrent forces *If forces act on different points of an object, these are non-concurrent forces

16. Newton’s Three Laws of Motion Newton’s First Law of Motion (Law of Inertia) “An object at rest remains at rest and an object in motion continues to move with constant velocity in a straight line.”

17. Newton’s Second Law of Motion (Law of Acceleration) “If a net force (resultant) acts on an object, it will be accelerated. The magnitude of the acceleration will be proportional to the net force and inversely proportional to the mass of the object and the direction of the acceleration will be in the same direction as the net force.”

18. Newton’s Third Law of Motion (Action-Reaction) “To every action, there is always an opposed and equal reaction.”

19. Equilibrium *no net change; balance *no translation or rotation *static equilibrium *dynamic equilibrium

20. First Condition of Equilibrium The resultant of forces acting on an object is zero. Two Conditions of Equilibrium

21. Second Condition of Equilibrium The sum of all the torques acting on an object is zero.

22. Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation

23. Find the tension in the cable and the magnitude and direction of compression exerted on the strut by the pivot in each of the ff. arrangements. Let the weight of the suspended object in each case be 1000N. Neglect the weight of the strut.

24. 1. 30 o

25. 2. 30 o

26. 3. 60 o 45 o

27. 4. 30 o 45 o

28. Find the Tension in the ropes A and B. 45 o A B 500 N

29. If the mass of the block is 5 kg, what is its weight? T = ?

30. If the weight of an object is 95 pounds, what is the mass in slug?