MOTION

1. MOTION

2. MOTION • Motion – the act or process of an object changing position. • How do we know when an object has moved? • After we have observed it for a given time, and recorded its location.

3. MOTION • 3 ways to measure (describe) motion • SPEED • VELOCITY • ACCELERATION

4. MOTION • SPEED = Distance / Time • Speed is a ratio • The relationship between how far the object traveled, and the time it took. • How far did it go in a given amount of time? • How long would it take to go a given distance?

5. MOTION • Since motion is rarely constant (uniform), we usually calculate average speed. • Notice • We measure distance • We measure time • We calculate speed On any trip, there will be times when you will be going fast, and times when you will be going slow. http://www.youtube.com/watch?v=iRxs379Vq_k&feature=related

6. MOTION • Speed = distance/ time = d/ t • units = meters/ second = m/ s • Practice Question • What is the average speed of a truck that makes a 120 km trip in 5 hours?

7. MOTION • Velocity – refers to the speed and direction of a moving object. • Speed = 60 m/s • Velocity = 60 m/s West • Velocity is a vector quantity (direction) • Speed is a scalar quantity (no direction)

8. MOTION • Acceleration – refers to a change in velocity. • Change in speed or • Change in direction • Change in direction is easy.

9. MOTION • Acceleration • Change in speed • = final velocity – initial velocity / time elapsed • = endspeed–beginningspeed / timeelapsed • units = meters/second/second • = m/s2 or

10. Motion • Acceleration = vf – vi • Practice Question • An object speeds up from 5 m/s to 15 m/s in 2 seconds. What is the object’s acceleration? t

11. MOTION • Acceleration • An object is travelling at 25 m/s. After 3 seconds the same object is travelling at 7 m/s. What is the object’s acceleration? • Slow down is negative acceleration • Deceleration

12. MOTION • Force is a push or pull that is capable of changing an object’s motion. • A push or pull • Measured in Newtons (N).

13. Motion • Inertia – the tendency of an object to remain in unchanging motion. • An object at rest will remain at rest, and an object in motion will remain in motion, until an unbalanced force acts on it. Newton’s 1st Law of Motion

14. MOTION • Friction always resists motion. • The force created by 2 things that are touching. Friction will cause the object to slow down or come to a stop. Bowling lanes are very smooth to limit friction.

15. MOTION • Air Resistance • The friction that air particles have on moving objects. It resists motion. • Also called Drag force.

16. MOTION • Free fall – when air resistance is not a factor, 2 objects will fall at the same rate. Air resistance would cause the feather to fall slowly. The bowling ball and the golf ball would hit the ground at the same time.

17. MOTION • Newton’s 2nd Law of Motion • The acceleration of an object is directly proportional to the net force acting on it, and inversely proportional to the mass of the object. • An object will change its motion in the direction of the unbalanced force that acts on it. The amount of change depends on the amount of force and the mass of the object. • Force = mass x acceleration ( F = m x a)

18. MOTION • Forces in exactly the same direction are added. 10 N 10 N 10 N OR 10 N net force = 20 N net force = 20 N

19. MOTION • Forces in exactly opposite directions are subtracted. 10 N 40 N 10 N 50 N OR net force = 30 N net force = 40 N

20. MOTION • Forces that are equal and in exactly opposite directions will cancel out. 40 N 40 N 50 N 50 N OR net force = 0 N net force = 0 N

21. MOTION • Forces that are not in exactly the same direction, or exactly opposite direction are more complicated. • There is a formula to combine these vectors. 40 N net force 40 N

22. MOTION • Newton’s 2nd Law of Motion • Practice Question • A rider and his bicycle have a combined mass of 75 Kg. How much force is required to cause them to accelerate 1 m/s2? • An unbalanced force of 20 N causes an object to accelerate 5 m/s2. What is the mass of the object?

23. MOTION • Momentum – the amount of force carried by a moving object. • Force = mass x velocity F = m x v Dump Truck Mass = 7,500 Kg Velocity = 900 m/s Sports car Mass = 1,200 Kg Velocity = 90,000 m/s What direction is the unbalanced momentum?

24. MOTION • Newton’s 3rd Law of Motion • Whenever two objects interact, the force exerted on one object is equal and in opposite direction to the force that acts on the other object.

25. MOTION • Projectile motion • A combination of vertical and horizontal motion.

26. MOTION • Centripetal force • The force that pulls an object out of its straight-line path into a circular path. • ‘Center – seeking’ Why is it possible to swing a bucket of water in a circle, and not let any of the water spill out?

27. MOTION • Gravity • The attractive force (pull) that exists between objects in the universe. • Any 2 objects have gravity. • Related to the masses of the two objects and the distance that separates them. m1 m2 distance

28. MOTION • Gravity favors massive objects. • Like the pull that Earth exerts on us. • Mass vs. Weight • Mass – the amount of matter in an object. • Never changes. • Weight – the force of gravity acting on an object. • Depends on gravity. • Weight = mass x gravity constant (w = m x g) • Measured in Newtons • Gravity constant = 9.8 m/s2

29. ENERGY • Work – refers to the force applied to an object and the distance that it travels. • Relationship / Ratio • Work = force x distance (w = f x d) • Measured in Joules (J) • Practice Question • A 15 Kg box is moved a distance of 20 meters. How much work is done?

30. ENERGY • Work • Units = Joules (J) • Joules is also the unit for energy • Work is related to the energy required to alter an object’s motion?

31. ENERGY • Power – the amount of work done in a given amount of time. • Relationship / Ratio • Power = work / time ( P = w/t ) • Measured in Watts (W) • The rate of energy use. • Practice Question • An electric lift can raise a 90 kg box to a height of 15 m in 3 seconds. What is the power of the lift?

32. ENERGY • Energy is the ability to do work. • Measured in Joules (J). • 2 Categories of energy • Potential Energy – stored (not in use) • Kinetic Energy – energy in use (energy of motion)

33. ENERGY • Potential energy due to location • Gravitational potential energy • PE = mass x gravity constant x height • (PE = m x g x h) • Gravity constant = 9.8 m/s2 Practice Question How much potential energy is stored in a 100 Kg object that is raised to 8 m? Whys is it easy to ski downhill?

34. ENERGY • Chemical potential energy • Stored in the bonds between atoms. • When chemical bonds are broken it releases energy. • When chemical bonds are formed it requires energy.

35. ENERGY • Kinetic energy • Energy that is in use. • Energy in motion. • KE = ½ mass x velocity 2 • KE = ½ m x v 2 • Practice Question • How much kinetic energy is in a 0.28 Kg bullet that is travelling at 40,000 m/s?

36. ENERGY • Energy conversions • Potential vs. Kinetic • 1. • 2. • 3. • 4. • 5. Why does the pendulum eventually stop?

37. ENERGY • Energy Forms • Chemical energy • Stored in the bonds between atoms in chemicals. Food Batteries Gasoline

38. ENERGY • Energy Forms • Mechanical energy • Energy of moving parts • Energy of machines Gears in a machine Sound Wind turbine

39. ENERGY • Energy Forms • Radiant energy • Energy that travels through space Heat (Infrared) Light (Solar) Electromagnetic spectrum

40. ENERGY • Energy Forms • Electrical energy • The flow of electrical charge through a conductor. Lightning Electricity

41. ENERGY • Energy Forms • Nuclear energy • Energy from interactions between the protons and neutrons in the nuclei of chemical atoms. Atomic nucleus contains protons (+) and neutrons. Nuclear power plant