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Motion

Motion. Motion. Change in position of an object Based on a reference point. Distance. How far an object has moved Units?. Displacement. Distance AND DIRECTION from the starting point. Example of calculating displacement.

danielgordon
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Motion

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  1. Motion

  2. Motion • Change in position of an object • Based on a reference point

  3. Distance • How far an object has moved • Units?

  4. Displacement • Distance AND DIRECTION from the starting point

  5. Example of calculating displacement If a runner runs 10 meters north, 4 meters east, 8 meters south and 4 meters west, what is his overall displacement?

  6. Speed How fast an object moves Distance an object travels over the time it takes Units?

  7. Average speed • The total distance traveled divided by the total time of travel

  8. Instantaneous Speed • The speed at any given point in time • Seen on the speedometer

  9. Equation for calculating speed Speed = distance/time

  10. Sample problem How fast is a car going if it traveled 24 miles in 30 minutes?

  11. Sample problem 2 How far can a car go in 5 hours if it is traveling at 65 miles/hour

  12. Sample problem 3 How long does it take to go 2 miles if you are walking 6 miles/hour?

  13. Velocity or speed Velocity includes a direction but other than that these two terms are fairly interchangeable

  14. Acceleration The rate of change of velocity Distance/time/time Units?

  15. Speeding up– positive accelerationSlowing down– negative acceleration

  16. Calculating Acceleration Acceleration = change in velocity / time Change in velocity = final velocity – initial velocity

  17. Sample Problems A swimmer speeds up from 1.1 m/s to 1.3 m/s during the last 20 s of a workout. What is the swimmers acceleration during this time interval?

  18. Sample problem 2 • A satellite's speed is 10,000 m/s. After 1 minute it is 5,000 m/s. What is the satellite’s acceleration?

  19. Graphing Motion • When you are graphing motion we graph the time on the x-axis and the distance on the y-axis • The slope of the line is the speed

  20. Positive slope • Object is moving away from the starting point

  21. Negative Slope Negative slope means the object is moving towards the starting point

  22. No Slope • The object is stopped

  23. Acceleration graphs– time vs. velocity and slope is acceleration

  24. Positive slope • Object is speeding up

  25. Negative Slope Object is slowing down

  26. No Slope • Object is maintaining a constant speed

  27. Force • Any push or pull that one body exerts on another • Not all forces are obvious… what forces are you exerting right now?

  28. Units on Force • Newtons • Named after Issac Newton the scientist who first studied forces and motion.

  29. Balanced forces • When forces are balanced their net force = 0 No change in motion when the forces are balanced

  30. Unbalanced Forces • You have to exert a unbalanced force on an object to get it to change its velocity (speed or direction)

  31. Calculating Net Force example problem In a tug of war the blue team is pulling with 25 N of force and the red team is pulling with 20 N of force, who is winning and what is the Net force on the rope?

  32. Newton’s First Law of Motion The law of Inertia-- An object in motion will stay in motion, an object at rest will stay at rest until a outside force acts upon it

  33. Inertia An objects resistance to change its motion Which has more inertia at rest? In motion?

  34. When is this law seen? CAR CRASHES!!!

  35. Newton’s second law of motion Force = mass x acceleration

  36. Sample problem You are pushing a friend on a sled. You push with a force of 40 N. Your friend and the sled together have a mass of 80 kg. Ignoring friction, what is the acceleration of your friend on the sled?

  37. If you add force and it accelerates what do you need to do just to keep an object in constant motion?

  38. Gravity Gravity is a constant force between any two objects of mass. It is usually so small we can ignore it, except for the gravity that Earth exerts on us.

  39. Acceleration due to gravity = 9.8 m/s2 ** The force due to gravity is considered your weight (it changes on the different planets with different gravities)

  40. Newton’s Third Law of Motion For every action there is an equal and opposite reaction If I push on the wall it pushes back on me

  41. Examples of Action-Reaction Rocket propulsion

  42. Friction The force that opposes motion between two surfaces

  43. Friction depends on two factors • What kind of surfaces are touching The rougher the surfaces the more friction 2. How much force is between the surfaces The more they are pushed together the greater the friction

  44. Causes of Friction The surface of even the smoothes materials are bumpy and the bumps get stuck on one another

  45. Types of Friction • Static Friction– The friction between two surfaces that are not moving Ex: A box sitting on the ground

  46. Types of friction cont. 2. Sliding Friction Forces that oppose the motion of something moving. When the force is removed this is the friction that eventually stops the object

  47. Types of friction cont. 3. Rolling Friction– The friction between a rolling object and the ground A car wheel and the ground This is why a car wheel doesn’t stay put on the ice!

  48. Types of Friction Cont. 4. Fluid Friction (Drag)– The friction due to an object moving through a fluid or gas The friction on a swimmer, race car

  49. Types of Friction Cont. 5. Air Resistance– Friction the atmosphere applies on an object (type of fluid friction)

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