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Finish Activity 73

Finish Activity 73. Follow procedure steps 3-7 Discuss in your groups and answer analysis questions 3-5. Review Student Sheet 73.1 Responses. Follow-up:. Major Concepts Making decisions often involves trade-offs-----giving up one thing to gain another.

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Finish Activity 73

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  1. Finish Activity 73 • Follow procedure steps 3-7 • Discuss in your groups and answer analysis questions 3-5

  2. Review Student Sheet 73.1 Responses

  3. Follow-up: • Major Concepts • Making decisions often involves trade-offs-----giving up one thing to gain another. • The potential for accidents and the existence of hazards impose the need for injury prevention and the need to understand the physics of how a car moves (force and motion)

  4. Analysis: • Compare the features you listed in Step 2 to the features listed on Student Sheet 73.1. How are they: • similar? • Answers will vary. Share responses. • different? • Answers will vary. Share responses.

  5. For each feature on Student Sheet 73.1 that you drew an “X” next to, explain why you decided it was less important. • Answers will vary. Share responses. • What factors other than safety do people consider when buying a car? • People typically consider looks (color, style), price, cargo size, how many passengers it can fit, and fuel economy.

  6. Do you think car features can: • reduce damage, injuries, and fatalities in car accidents? Explain. • Possible answer- Features such as seat belts or airbags reduce the effects of accidents by padding the impact. A more sturdy frame and/or internal roll bar car protect the passenger in a rollover. • prevent accidents? Explain. • Possible answer- Brakes that function well or mirrors and visors that improve a driver’s ability to see can prevent accidents. Less height can prevent rollovers and better handling (or greater acceleration) can help a driver avoid accidents.

  7. Which vehicle do you think is safer- Vehicle 1 or Vehicle 2? Explain what data convinces you that this vehicle is safer than the other one. • Vehicle 1 has a greater height and mass, lower top speed, and slower acceleration. This would make it safer, especially for the 15-24 year old group since they would not be able to go as fast and would have more mass to protect them in a collision. • Based on the number of airbags and shorter stopping distance, vehicle 2 is safer. It protects more people due to the airbags and can respond more quickly (stopping and accelerated) to help avoid accidents.

  8. Activity 74 Title: Measuring Speed

  9. Background Information: • Speed • An object in motion takes time to change its position. Speed is the measurement of the rate of change in position and can be linear or rotational. The units for speed are a distance or an angle per unit of time, such as miles per hour or degrees per second. • Velocity • Speed (s) and velocity (v) are related concepts but are not the same thing. The velocity of an object includes both its speed and its direction.

  10. Speed vs. Velocity • What is the difference? The velocity of an object includes both its speed and its direction.

  11. More vocabulary • tested variable: the variable that is manipulated (changed) in an experiment • controlled variables: the variables that are not changed in an experiment.  also called "controls“ or independent variable. • responding variable: the variable you are measuring in an experiment. Also called dependent variable.

  12. What things can contribute to a car accident? • Speeding or going too fast • In the United States, car speed is typically measured in mph. • km/h is used for car speed in other countries. • Scientists often measure everyday speeds in m/s. • Today, we will measure speed in cm/s.

  13. Read E-7 Part A Problem: How can you measure the speed of a moving cart? Hypothesis Part A: If you ______________, then you can ______________________.

  14. How do people measure speed? • Speedometer • Radar Gun • Total Distance/Total Time

  15. Procedure • Step #8 – Why do you use three trials? • Watch for ERROR. What is this? • Timing errors may cause the time to be too long or too short. • You may stop the watch too soon, and sometimes too late. • Your reaction time may effect the timing. • Taking the average of 3 trials can limit the error. • You may need to do an addition trial if one is too far off from the others.

  16. Minimize Errors • Release the cart the same way each time. • Try to get data the is ACCURATE and REPRODUCIBLE. • If you get 10 m/s, 11 m/s, and 25 m/s, you may want to redo the third trial. • Put a book to stop the cart. The cart SHOULD NOT roll off the table.

  17. Data/Evidence: Always include units Average

  18. Part A Discussion • What is a variable? A variable is what we change, measure and control in an experiment. They are the factors that influence the speed of the cart. • What variable did we test? There was no tested variable. You did not change or manipulate any factors. • What variables did we control? the track (release height, angle & surface) the cart’s mass

  19. Part B Problem: What will happen to the speed of the cart if we change the release height of the cart? Hypothesis: If you lower the release height of the cart, then ____________________.

  20. How will you test your hypothesis? Write a procedure to test your hypothesis. How many trials? What are your variables other than height?

  21. Data/Evidence: Make 3 tables, one for each release height (A, B, and C). Measure the time over 50 cm. Make sure you title your tables. Ex.: Release height A Release height B Release height C

  22. Calculating Speed Why did we use the “average value”? What does it mean if your data is accurate? What does it mean if your data is reproducible? Why are these qualities important to scientists?

  23. Calculating Speed Speed = distance traveled / time What units did we use in this lab? What units would you use to measure the speed a car travels? What units would you use to measure the rate at which your hair grows?

  24. Speed = Distance/Time • What is the speed of a car that travels • 100 miles in 2 hours? • 50 MPH • What is the speed of a car that travels 30 kilometers in 1/2 hour? • 60 km/h

  25. What was the tested variable? The height of the release of the cart. This was the variable we changed or manipulated. • What variable was time? • Was there a different controlled variable in part B?

  26. Discuss Analysis 1-3 with your group • According to your data from part A, what is the speed of the cart? • According to your data from part B, what is the effect of release height on speed? 3. List some common units for speed. Why are there so many different units?

  27. Analysis Question #3 • List some common units for speed. Why are there so many different units? • miles per hour (MPH) • kilometers per hour (kph or km/h) • meters per second (m/s) • Different speed units are used because there are many different units for distance and time, and some units are more convenient to use than others in different situations.

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