1. Balanced and Unbalanced Forces Mr. Hastings Physical Science Prescott High School

2. What is a force? 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

3. SI UNIT of FORCE Forces can be measured in pounds, tons, or newtons. The NEWTON is the SI unit of force so is also what will be used for this class. 1 newton = 1 kg*1m/s 2

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

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

6. Balanced Forces Balanced forces do not cause change in motion They are equal in size and opposite in direction https://www.youtube.com/watch?v=Jra XtL9d-uk https://www.youtube.com/watch?v=Jra XtL9d-uk

7. Unbalanced Forces An unbalanced force always causes a change in motion When unbalanced forces act in opposite directions you can find the net force by vector addition.  Net force Magnitude  The sum of the two forces with opposite directions being opposite signs. Direction  Direction of the sign or of the largest force ://www.youtube.com/watchttpsh?v=gSTpJXSkL EU ://www.youtube.com/watchttpsh?v=gSTpJXSkL EU

8. Unbalanced Forces 3 N, right + (– 6 N), left = 3N, left

9. Unbalanced Forces 4 N, left + ( – 10 N), right = 6N, right

10. Unbalanced Forces 5 N, right + 10 N, right =15N, right

11. FRICTION Friction is a force that opposes the motion of objects that touch as they move past each other. All moving objects are subject to friction. There are 4 main types: static, sliding, rolling, and fluid friction.

12. STATIC FRICTION The friction force that acts on objects that are not moving Always acts in the direction opposite of the applied force Strongest friction force.

13. SLIDING FRICTION The friction force that opposes the motion of an object as it slides over a surface. Not as strong as static friction.

14. ROLLING FRICTION The friction force that acts on rolling objects. Not as strong as sliding friction.

15. FLUID FRICTION The friction force that opposes the motion of an object as it moves through a fluid. The weakest friction force.

16. ASSIGNMENT Take out a clean sheet of paper and write a compare/contrast of the 4 types of friction. Turn in before you leave.