1. Balanced and Unbalanced Forces
11/17/15
Title
Date
Paga

2. Friction
Friction – a force that opposes motion exerted by surfaces in contact.

3. Static friction
Static friction is friction between two or more solid objects that are not moving relative to each other. For example, static friction can prevent an object from sliding down a sloped surface.

4. Static Friction
Static Friction – the force that opposes the start of motion.
Adjustable force – as the applied force increases, static friction increases.
Always equal but opposite to the applied force until a maximum is reached
Maximum Static friction – equal to the minimum force required to start the objects motion.

6. Balanced and Unbalanced Forces
A force is a push or pull that causes an object to move, stop, or change direction
In physics a force is anything that makes an object accelerate

7. Force Forces come in pairs Forces have a magnitude and a direction
Magnitude: 5N
Direction: north (up)
5N, north (up)

8. Balanced and Unbalanced Forces
Forces occur in pairs and they can be either balanced or unbalanced

9. Balanced Forces Balanced forces do not cause change in motion
They are equal in size and opposite in direction

10. Unbalanced Forces An unbalanced force always causes a change in motion
When unbalanced forces act in opposite directions you can find the net force
Net force
Magnitude
The difference between the two forces
Direction
Direction of the largest force

11. Unbalanced Forces
30 N, right – 60 N, left = 30N, left

12. Unbalanced Forces
4 N, left – 10 N, right =
6N, right

13. Unbalanced Forces
25 N, right + 50 N, right =
75N, right

14. = The sum of forces = Fnet
Objects Accelerate in the direction of the net force

16. Force Diagram Practice
Title Date Page

18. Sky Diver in free fall Ff Friction force on Diver by Air
Fg Gravitational force on diver
by earth

19. A book sitting on a table (at rest). Diagram the forces on the book.

20. Book on the table Fn Normal force on book by table
Fg Gravitational force on book
by earth

21. Bull Dog pushing a skate board
Bull Dog pushing a skate board. Diagram the forces acting on the skateboard.

22. Skateboard pushed by dog
FN Normal force on skateboard by street
Ff friction force on skateboard by street
Fp Pushing force on skateboard by dog
Fg Dog + Fg skateboard
gravitational force on skate board by earth

23. Dog on Ramp
At rest

24. FN Normal force on dog by ramp
Dog on ramp
FN Normal force on dog by ramp
friction force on dog by ramp Ff Fg
gravitational force on dog by earth

26. FT Tension force on climber by rope FN Normal force on climber by rock
Forces on Rock Climber
FT Tension force on climber by rope
FN Normal force on climber by rock
Fg Gravitational force on Climber by earth

28. Ff friction force on ball by
Forces on Foot Ball
Ff friction force on ball by
air resistance f
Fg Gravitational force on Ball by earth