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Scientific Method

Scientific Method. Chapter 1.2. What is an experiment?. A situation where we observe what happens. Start with a question to be answered. Usually an experiment is designed to provide data that can be analyzed. You do experiments everyday. Why won’t the car start?

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Scientific Method

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  1. Scientific Method Chapter 1.2

  2. What is an experiment? • A situation where we observe what happens. • Start with a question to be answered. • Usually an experiment is designed to provide data that can be analyzed.

  3. You do experiments everyday. • Why won’t the car start? • The VCR won’t record my show!

  4. Scientific Evidence • Observations from an experiment that can be repeated with the same result at a later time.

  5. The Scientific Method • Ask a question. • Formulate a hypothesis. • Design and conduct an experiment. • Collect and Analyze Data. • Make a Tentative Conclusion • Test Conclusion.

  6. Variables • Experimental Variable (Independent variable) • The variable that the experimentor changes. • Control Variable • The variables in an experiment that you keep the same in every group.

  7. Controlled Experiment • You can only change one variable at a time in an experiment. • VCR example • If you change more than one variable you will not know what caused the change.

  8. Experimental Protocol • Many Trials to find an average. • Do not want to use extremes • Experimental Technique • Do the experiment the same way every time. • Procedures that can be replicated. • The procedure the is designed should be so accurate that anyone anywhere can reproduce the results.

  9. Motion

  10. What is Motion??? • A change in position.

  11. Speed • Rate of Change in Position. • “Rate of Motion” • Types of Speed • Instantaneous • Constant • Average

  12. Instantaneous Speed • The rate of motion at a given instant. • A speedometer in a car shows the instantaneous speed of the car.

  13. Constant Speed • A speed that does not change over a period of time. • Cruise Control in a car.

  14. Average Speed • On a trip from Chicago to Texas could you stay the same speed? • Could get an average of all the speeds during the trip. • The total distance of the trip divided by the total time of travel.

  15. Velocity Notes 3.2

  16. What is Velocity? • Describes the motionand the direction. • Even if speed remains the same, if the direction changes then the velocity has changed.

  17. Calculating Average Speed / Velocity • d= distance • v= speed / velocity • t= time

  18. Equations for Speed and Velocity • V = d / t • D = v  t • T = d / v

  19. Sample Speed / Velocity Problems • A car travels a distance of 16 m in 1.8 seconds. What is it’s speed? • V = d/t V = 16m / 1.8s V = 8.89 m/s

  20. Sample Speed / Velocity Problems • Sound travels at a speed of 330 m/s. If a lightning bolt strikes the ground 1 km away from you, how long will it take for the sound to reach you? • T = d/v T = 1km / 330m/s T = 1000m / 330m/s T = 3.03 s

  21. What is Acceleration? • The rate of change of velocity. • Car commericial  0 to 60 mph in 10 seconds. • Speeding up • The amount of change in velocity in a time interval.

  22. How to Calculate Acceleration?  means “change in”

  23. Practice Problems • A car’s velocity changes from 0 m/s to 30 m/s in 10 seconds. Calculate the car’s average acceleration. • A = V / t A = 30 m/s – 0m/s / 10s – 0s A = 30 m/s / 10s A = 3 m/s/s or 3 m/s2

  24. Practice Problems • A swimmer speeds up from 1.1 m/s to 1.3 m/s during the last 20 s of the workout. What is the acceleration during this interval? • A = V / t A = 1.3 m/s – 1.1 m/s / 20s – 0s A = 0.2 m/s / 20s A = 0.01 m/s/s or m/s2

  25. Graphing Motion

  26. Forces Newton’s First Law

  27. What is a Force? • A push or pull on an object. • Some forces are seen, for example a box being pushed across the table. • Some forces are not seen, for example the floor pushing up on your feet.

  28. Balanced Forces • A balanced force is a force on an object that is equal in size and opposite in direction. • Tug of war is a good example. • Each person is pulling on the other with an equal and balanced force.

  29. Unbalanced Forces • Sometimes forces are not equal or opposite. • Example: Pushing a car. • An unbalanced force is a net force. • A net force acting on an object will change the velocity and/or direction.

  30. Why do objects stand still if no force is applied? • Inertia! • The tendency of objects to resist a change in motion. • If it is moving – it will keep moving. • If it is still – it will not move. • UNLESS….. A net forceacts on it!

  31. Inertia • Examples: • A book on your desk will sit there and not move, unless you apply a force to the book to move it. If your arm pushed the book, that would be a force. • If you drive in a car and hit a wall without the force of a seat belt to stop you, your body will continue to move even though the car has stopped. This is why people go through the windshield.

  32. Which object has more inertia? • Heavier objects are harder to stop moving and start moving. • The larger the mass, the greater the inertia. • Example: A semi truck is harder to stop than a toy truck.

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