1. Physics Day 42 – FBD -LO: FBD with numbers -LO: FBD for Static problems AGENDA Do Now Finish WS1 Notes Do Now – 1. Please draw a Free Body Diagram of a 5kg book lying on a table being pulled by a string to the right with a force of 3N. (not moving)

2. What is force do? How do we change motion in velocity or only direction? Why some objects accelerate at higher rates than others do? A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. Forces cause changes in velocity over time, or accelerations.

3. Type of forces Contact Forces Frictional Force Tension Force Normal Force Air Resistance Force Applied Force Spring Force

4. Type of forces Action-at-a-Distance Forces Gravitational Force Electrical Force Magnetic Force

5. Normal Forces Physics Book Table

6. Normal Forces Physics Book Table a = 0 FgFg FnFn

7. Friction Physics Book Table a = 0, v = 0 FgFg FnFn The force of friction is zero because the book is not trying to slide in any direction. If you put a friction force in, it would be unbalanced and cause an acceleration (and that never happens)

8. Friction Physics Book Table String tied to book

9. Friction Physics Book Table a = 0 (constant velocity to the right) FgFg FnFn F string String tied to book FµFµ

10. Equilibrium and Statics When all the forces that act upon an object are balanced, then the object is said to be in a state of equilibrium.act The forces are considered to be balanced if the rightward forces are balanced by the leftward forces and the upward forces are balanced by the downward forces.

11. Determining the Net Force An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. unbalanced force

12. Spring Forces Stretched spring Fs< 0 Equilibrium Fs=0

16. 4.00 kg

19. The object hung from the cable has a weight of 25 N. Write the equation for the sum of the forces in the y-direction. What is the tension in the cable? Repeat the problem above with a 5 degree angle. How does the tension compare?

20. 2TSin30 = 25N T=25N

22. T 2 Cos30 = 30N T 2 Sin30 = T 1 T 2 = 2*T 1 T 2 = 30N/0.87 T 2 = 34.5N T 1 = 69N

24. Use g = 10 m/s/s W=mg = 20 kg * 10 m/s/s = 200N Fn = mgCos30 = 200N*cos30 = 174N How did we do that?