Physics On the Road - Lesson 8

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Physics On the Road - Lesson 8

  1. 1. Falling down Physics On the Road Lesson 8
  2. 2. LI… Describe free fall. Use kinematic equations to make predictions Explain parabolic projectile motion.
  3. 3. Free fall
  4. 4. Gravity is uniform acceleration  Galileo first proposed the idea that all objects fall with uniform acceleration.  He proved it by rolling balls down slopes  It is an idea with far reaching implicationsGravity accelerates all objects on Earth at a rate of 9.8 ms-2
  5. 5. Air resistance  Why doesn’t it look like all objects fall at the same rate.  Gravity is not the only force acting.  Air resistance acts against motion. The air resistance depends upon size, shape but mostly speed.
  6. 6. Falling down  Describe a parachute jump using a velocity time graph. time velocity
  7. 7. Still falling down  Explaining a parachute jump  Use the idea of forces time velocity w w w f w f w f
  8. 8. Ignore air resistance - constant acceleration ∆v ∆t ∆t t=0 2∆v If you ignore air resistance falling objects gain speed at the same rate. They accelerate at Earth at a rate of 9.8 ms-2. Q1. How far will a coin fall in 5 seconds? 0 ms-1 9.8 ms-1 19.6 ms-1
  9. 9. Sideways makes no difference ∆v ∆t ∆t t=0 2∆v 0 ms-1 9.8 ms-1 19.6 ms-1 ∆v 2∆v 9.8 ms-1 19.6 ms-1
  10. 10. Changing velocity in a parabolic path -vectors v ∆v v v v v v Due to gravity v ∆v new v v ∆vnew v
  11. 11. Demonstrate Your Understanding Explain why this trick is not as dangerous as it looks. EXTENDED ANSWER TASK Use diagrams Use principles Use vectors Use calculations

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