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Falling objects

Falling objects. This morning. You jumped out of bed, walked in to the bathroom, and climbed on to the scales. What were you measuring?. Homework. Complete the homework sheet “Force and acceleration calculations”. Previously. Answers. a) 560 N b) 2.5 m/s 2 c) 20 000 kg d) 40 000 N.

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Falling objects

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  1. Falling objects

  2. This morning • You jumped out of bed, walked in to the bathroom, and climbed on to the scales. • What were you measuring?

  3. Homework Complete the homework sheet “Force and acceleration calculations”. Previously...

  4. Answers • a) 560 N b) 2.5 m/s2 c) 20 000 kg d) 40 000 N. 2. b) 3000 N. • a) ii) 16 N b) i) 0.4 m/s2 ii) 32 N in the opposite direction to her direction of motion.

  5. Open your books...Date:Title:LO: Falling objects To learn about objects falling through fluids. Don’t forget: Underline the title and date with a ruler!

  6. Outcomes: • You must be able to describe the forces acting on an object when falling through a fluid. • You should be able to explain how this affects acceleration of the object. • You could be able to explain why an object reaches terminal velocity and describe some of the factors that determine this velocity.

  7. From the textbook • Read pages 204-205 in full. • Copy the “Key points” box. • Sketch the diagrams and graph in figure 2.

  8. Hammer and Feather Experiment • If both dropped from the same height, which one will hit the floor first, and why? • If they are both put in a sealed container, which one will hit the floor first this time, and why?

  9. Galileo Galilei. Born 1564 • Galileo proposed that a falling body would fall with a uniform acceleration, as long as the resistance of the medium through which it was falling remained negligible, or in the limiting case of its falling through a vacuum.

  10. Then in 1971 Commander David Scott went to the moon: • They decided to try the hammer and feather experiment... But what happened?

  11. David Scott dropping the hammer and feather on the moon: • Proved that Galileo was correct in his predictions. • But it took nearly 300 years to demonstrate it!

  12. Complete the worksheet (10 minutes)

  13. The Hammer and the Feather Answers • a) 2.2 kg b) 22.6 kg 2. a) 0.05 N b) 0.29 N 3. a) Faster b) There is a bigger force on the hammer on Earth than on the Moon c) Slower d) Air resistance slows it down • Drop them in a vacuum

  14. Watch the Video clip • Terminal Velocity

  15. Terminal velocity of a skydiver

  16. Velocity–time graph of skydiver

  17. Homework None today!

  18. Final thoughts • We said that the gravitational field strength is also the acceleration due to free-fall. • On Earth this is approximately 10 N/kg or 10 m/s2. • If a ball is dropped from a tower, can you calculate the speed of the ball after 3 seconds? Speed = Acceleration X Time = 10 m/s2 X 3 Sec = 30 m/s

  19. Outcomes: • You must be able to describe the forces acting on an object when falling through a fluid. • You should be able to explain how this affects acceleration of the object. • You could be able to explain why an object reaches terminal velocity and describe some of the factors that determine this velocity.

  20. Have a great day!

  21. Resources • WSR worksheet “Hammer and the feather”. • Small hammer, Feather & 2 containers to put them in (i.e. Shoe box or plastic sweet jar) • 2 x Large plastic measuring cylinders • 2 x large ball-bearings

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