1. Statics Force is a push or pull caused by the interaction between two objects. Forces that do not cause motion are defined by the laws of Statics.

2. Answer Me!!! Do all forces cause motion? Think of an example of a force that does not cause an object to go into motion. Do all forces cause motion? Think of an example of a force that does not cause an object to go into motion.

3. Equilibrium When two or more forces are in perfect balance, they will cancel each other out. This is called a state of equilibrium. When two or more forces are in perfect balance, they will cancel each other out. This is called a state of equilibrium.

4. Practice Problem Draw the free-body diagram for a book on a desk. Draw the free-body diagram for a book on a desk. Book

5. Practice Problem Draw a free-body diagram of the desk as I push on it. Draw a free-body diagram of the desk as I push on it.

6. Practice Problem Draw the free body diagram of the object sitting on top of the book Draw the free body diagram of the object sitting on top of the book

7. Final Thought… Draw a free body diagram of the book. Draw a free body diagram of the book.

8. Answer Me!!! What would these spring scales read? What would these spring scales read? 10N

9. Force Vectors A vector quantity is a measurement that represents both magnitude and direction. A vector quantity is a measurement that represents both magnitude and direction. A scalar quantity can be described by magnitude only. A scalar quantity can be described by magnitude only. Force is a vector quantity. Forces are measured in Newtons (N). Force is a vector quantity. Forces are measured in Newtons (N).

10. Combining Vectors When more than one force acts on a body, they can be combined to form a resultant vector. When more than one force acts on a body, they can be combined to form a resultant vector. Combining parallel forces is as easy as adding (or subtracting) the magnitudes of each vector. Combining parallel forces is as easy as adding (or subtracting) the magnitudes of each vector.

11. Practice Problem Two teams are engaged in a tug of war. Team A pulls to the right with a force of 2500 N. Team B pulls to the left with a force of 2000 N. What is the resultant force on the rope? Two teams are engaged in a tug of war. Team A pulls to the right with a force of 2500 N. Team B pulls to the left with a force of 2000 N. What is the resultant force on the rope?

12. Parallelogram Rule To find the resultant of two non- parallel vectors, construct a parallelogram where the two vectors are sides. To find the resultant of two non- parallel vectors, construct a parallelogram where the two vectors are sides. The diagonal will be the resultant. The diagonal will be the resultant. An arrow of the same length in the opposite direction as the resultant is called the equilibrant. An arrow of the same length in the opposite direction as the resultant is called the equilibrant.

13. Practice Problem Find the resultant of the two concurrent forces. Find the resultant of the two concurrent forces. 19 N 13 N

14. Practice Problem Find the resultant of the two concurrent forces. Find the resultant of the two concurrent forces. 10 N 20 N

15. Composition of Forces When two vectors are applied at 90 o, you can use right triangle geometry to calculate the resultant force. When two vectors are applied at 90 o, you can use right triangle geometry to calculate the resultant force. 13 N 17 N

16. Answer Me!!! Two forces are applied to an object concurrently (at the same time). Two forces are applied to an object concurrently (at the same time). –What angle will produce the greatest resultant force? –What angle will produce the least resultant force?

17. Answer Me!!! A 15 N force due north and a 12 N force due east act concurrently on an object. What is the resultant force acting on this object? A 15 N force due north and a 12 N force due east act concurrently on an object. What is the resultant force acting on this object?

18. Answer Me!!! A bushel basket holds about 125 medium apples. How much will this basket weigh? Will it be difficult to lift? A bushel basket holds about 125 medium apples. How much will this basket weigh? Will it be difficult to lift?

19. Resolution of Forces One force acting on an object can be broken into perpendicular components using trigonometry. One force acting on an object can be broken into perpendicular components using trigonometry. F = 10N F x = F cos  F y = F sin 

20. Practice Problem A 20 N force is applied to a block at an angle of 35 o above horizontal. What are the vertical and horizontal components of this force? A 20 N force is applied to a block at an angle of 35 o above horizontal. What are the vertical and horizontal components of this force?

21. Practice Problem A 20N block is placed on top of an incline that is 20 o above horizontal. How much force is gravity exerting on the block that is directed down the incline? A 20N block is placed on top of an incline that is 20 o above horizontal. How much force is gravity exerting on the block that is directed down the incline? 20 o

22. Final Thought… A wagon is pulled along a level sidewalk with a force of 100N. If the wagon handle is at an angle of 37 o, how much of that force is pulling the wagon horizontally? A wagon is pulled along a level sidewalk with a force of 100N. If the wagon handle is at an angle of 37 o, how much of that force is pulling the wagon horizontally?