An Introduction to Forces

1. An Introduction to Forces Definition: A force is a push or a pull in a particular direction.

2. How does it balance?Textbook p. 53 • You probably would be uneasy standing under Balanced Rock near Buhl, Idaho. Yet this unusual rock stays in place year after year. The rock has forces acting on it. So, why doesn’t it fall over? • Answer: The forces acting on the rock combine, and the rock does not move. Now, let’s read page 54.

3. Remember… A force is a push or pull in a particular direction.Forces Packet p. 1 EXAMPLE of a PUSH: When you ride a bike, your foot pushes against the pedal. The push makes the wheels of the bike move. EXAMPLE of a PULL: When you drop something, it is pulled to the ground by gravity.

4. Push or Pull • Push • Push • Push • Pull (gravity) • Push & Pull

5. Remember…Textbook p. 54, Review from Ch. 2- Lesson 1 There are contact forces. Example: Air Resistance, pushing a shopping cart, pulling on a rope in Tug’o’War There are non-contact forces. Example: Gravity, magnetism, static electricity

6. The Big Ideas…Forces Packet p. 1 • Forces can make objects: • start moving. • move faster. • move slower. • stop moving. • change direction. • change an objects shape.

7. REMEMBER…Forces Packet p. 1 Velocity is the speed and direction of a moving object. Acceleration is the measure of the change in velocity during a period of time. FORCES CAUSE ACCELERATION!

8. Force Facts…Forces Packet p. 1 • Forces are measured in Newtons (N) • A Newtonis equal to the amount of force required to accelerate a mass ofone kilogram at a rate of one meter per second • Forces come in pairs. • Forces act in a particular direction. • Forces usually cannot be seen, but their effects can be seen.

9. For the next few slides:Label each picture as a push or pull. Forces Packet p. 2

10. Combining ForcesTextbook p. 55-56, Forces Packet p. 3 Net Force: The combination of all the forces acting on a object. Forces may work together. This means the forces act in the same direction. Forces may be opposite forces. This means the forces act in opposite directions.

11. Balanced and Unbalanced ForcesTextbook p. 56, Forces Packet p. 3 Balanced Forces: Balanced forces do not cause a change in motion. net force of zero. • Unbalanced Forces: • Unbalanced forces cause a change in motion. • net force that is not zero.

12. Balanced Forces

13. Unbalanced Forces

14. Circle the best answer. The forces above are showing PUSHING/PULLING forces. The forces above are WORKING TOGETHER/OPPOSITE forces. The forces are EQUAL/NOT EQUAL. The forces DO/DO NOT balance each other. The resultant force is 1000N TO THE LEFT, 1000 N TO THE RIGHT, or ZERO. There IS/IS NO motion. Forces Packet p. 4

15. Answers: • The forces above are showing PUSHING/PULLINGforces. • The forces above are WORKING TOGETHER/OPPOSITEforces. • The forces are EQUAL/NOT EQUAL. • The forces DO/DO NOT balance each other. • The resultant force is 1000N TO THE LEFT, 1000 N TO THE RIGHT, or ZERO. • There IS/IS NO motion. Forces Packet p. 4

16. Circle the best answer. 7. The forces shown above are PUSHING/PULLING forces. 8. The forces shown above are WORKING TOGETHER/OPPOSITE forces. 9. The forces are EQUAL/NOT EQUAL. 10. The forces DO/DO NOT balance each other. 11. The stronger force is pulling to the RIGHT/LEFT. 12. The weaker force is pulling to the RIGHT/LEFT. 13. The motion is to the RIGHT/LEFT. Forces Packet p. 5

17. Answers: 7. The forces shown above are PUSHING/PULLINGforces. 8. The forces shown above are WORKING TOGETHER/OPPOSITE forces. 9. The forces are EQUAL/ NOT EQUAL. 10. The forces DO/ DO NOT balance each other. 11. The stronger force is pulling to theRIGHT/ LEFT. 12. The weaker force is pulling to the RIGHT / LEFT. 13. The motion is to the RIGHT/LEFT. Forces Packet p. 5