Newton’s Laws of Motion

1. Newton’s Laws of Motion How and why do things move the way they do?

2. Motion • In order to prove motion, you must first have a point of reference. • You don’t have to see something move, you can tell something has moved by its position according to a reference point. • Not all motion is as obvious. You are in motion now, not relative to this room or your desk, but relative to other planets.

3. Distance vs displacement • When judging motion or position, you must understand the difference between distance and displacement. • Distance is how far an object has moved. • Displacement is the distance from the starting point. • You can travel a distance of 50 meters and have a displacement of 0.

4. Speed • Speed is the determined using the total distance traveled by the total time it takes. S=d/t

5. Velocity • Velocity is speed in a given direction. • The formula is the same as the formula for speed. S=d/t • Where would velocity be needed?

6. Acceleration • Acceleration is the rate of change in velocity divided by the amount of time it takes. (final velocity – initial velocity) Time

7. Motion and Forces • Force is any push or pull • Balanced force causes no change in motion. The net force would be equal to zero. • Unbalanced force will cause a change in motion. The net force is equal the difference between the forces if they are in opposite directions, or added if the forces are in the same direction.

8. Inertia • Inertia is the resistance of an object to change its motion. • Mass is the amount of matter in an object. • The greater the mass, • the greater the inertia. • The greater the inertia, • the greater the mass.

9. Newton’s First Law of Motion • The Law of Inertia states that an object in motion stays in motion, unless acted upon by an outside force. • Law 1

10. Newton’s second law of motion • How mass, force, and acceleration are connected. • The net force of an object causes the object to accelerate in the direction of the net force. • a is acceleration, F is net force, and m is mass. a = F m

11. Acceleration • There are two formulas for acceleration • 1. (final velocity – initial velocity) time • 2. F(force) • m (mass) The formula you use depends on the information that you are given.

12. Friction • According to Newton’s first Law, without any opposing forces motion or lack of motion would remain the same. • One force that opposes motion is friction. • Friction increases/decreases depending on the type of surfaces. • The stronger the force pushing the surfaces together, the stronger the microwelds. • Microwelds are surface bumps.

13. Static Friction • If the microwelds that form between the surface and an object trying to be moved are to tight to be broken, then you have static friction. • Static friction has no net force, therefore there is no acceleration.

14. Sliding friction • Sliding friction is the force that opposes the motion of two surfaces sliding past each other. • Sliding friction is caused by microwelds constantly breaking and then forming again as the object slides. • To keep the object moving, you must continue applying the force, if you don’t it will stop.

15. Rolling Friction • Rolling friction is the friction between a rolling object and the surface it rolls on. • Microwelds break and then reform as it rolls. • Rolling friction is usually much less than static or sliding friction.

16. Air Resistance • Air resistance affects anything that moves in the air. • Air resistance acts in the opposite direction of gravity. • The amount of air resistance depends on the size, speed, and shape of the object. • Which falls faster a feather • or an acorn?

17. The Law of Gravitation • Anything that has mass is attracted by the force of gravity. • Gravity is affected by the mass of an object, as well as the distance between the objects. • The greater the mass, the greater the force. • The greater the distance, the less the force.

18. Gravitational Acceleration • Near the Earth’s surface the gravitational attraction cause objects to accelerate at the rate of 9.8m/s2 • According to Newton’s second law of motion, force, mass, and acceleration are related according to the following formula • F=ma

19. Gravitational Acceleration • According to the second law, the force of an object that has an acceleration of 9.8m/s2 is as follows- • F= m x 9.8m/s2 • This force depends on an objects mass.

20. Weight • Weight is a response to the amount of gravity. • Since the gravitational force is the same as the weight of an object, the equation- • F= m x 9.8m/s2 • can also be written- • W= m x 9.8m/s2 • What would happen to your weight as you get farther away from Earth’s surface?

21. Weight and Mass • Since mass is the amount of matter in an object, and weight is the force of gravity on an object, • 1. How does your mass change on the moon? • 2. How does your weight change on the moon?

22. Projectile motion • A projectile is anything thrown or shot through the air. • Knowing what you do about the gravitational force, when shooting at a target like a dart board, where should you aim?

23. Vertical and Horizontal Motion • Throwing a ball is horizontal motion. • Dropping a ball is vertical motion. • Throwing a ball forward it always lands on the ground eventually. Why?

24. Centripetal Force • Acceleration towards the center of a curved or circular path, is centripetal acceleration. • When a car rounds a corner, • centripetal force is the friction • between the tires and the road. • Planets traveling around the sunhave centripetal force. • Explain why.

25. Newton’s Third Law of Motion • Action/Reaction • For every action in nature there is a reaction. • If action and reaction forces are equal and opposite, why or how is there motion.

26. Momentum • Momentum is the force needed to change motion. • To determine momentum, you take the mass of an object • times the velocity of an object. • Momentum is given the symbol p • p=m x v

27. Law of conservation of momentum • According to Newton’s Laws, momentum can’t be lost or gained, only transferred. • What does this mean?

28. Review • 1. An object in motion remains in motion unless acted upon by an outside force. • 2. Acceleration is the net force of an object divided by the mass of an object. • 3. For every action there is an equal and opposite reaction. • Let’s see it again!

29. How do these affect us in everyday life? • Now that you know these laws, here are some ways that they affect us in everyday life. • Show me! • Can you think of examples?