1. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Multiple-Choice Questions Animals Falling Cats

2. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats Question 1 Which is the correct free body diagram for a cat immediately after falling off of a cliff? b)a) c)

3. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats b)a) c) Force of Gravity is constant. D= ¼ A v 2, so D increases as v increases Which is the correct free body diagram for a cat immediately after falling off of a cliff? Question 1 Solution

4. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats Which is the correct free body diagram for a cat that has reached terminal velocity ? Question 2 b)a) c)

5. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats b)a) c) For v = v term, D = F g Question 2 Solution Which is the correct free body diagram for a cat that has reached terminal velocity ?

6. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats Question 3 An object with smaller cross sectional area A has a larger terminal velocity than an object with larger A. a) always true b) sometimes true c) never true

7. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats An object with smaller cross sectional area A has a larger terminal velocity than an object with larger A. a) always true b) sometimes true c) never true Need to compare the ratio (m/A), not just A alone. (Note: It will also depend on how aerodynamic the objects are in case there is a big difference in their drag coefficients.) Question 3 Solution

8. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats Question 4 Which of the following describes what happens to a meteor crashing through the atmosphere travelling faster than its terminal velocity? a) The meteor decelerates b) The meteor stays at constant v c) The meteor accelerates

9. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats Which of the following describes what happens to a meteor crashing through the atmosphere travelling faster than its terminal velocity? a) The meteor decelerates b) The meteor stays at constant v c) The meteor accelerates When v > v term, the drag force is larger than the gravitational force meaning the net force is opposite to the motion causing deceleration until v = v term. (Note: The work done by the drag force is converted into heat, which usually causes meteorites to burn up in the atmosphere.) Question 4 Solution

10. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats v air v bike Question 5 a) D = ¼  A (v bike ) 2 c) D = ¼  A (v bike + v air ) 2 b) D = ¼  A (v bike -v air ) 2 The magnitude of the drag on a cyclist encountering a head wind is given by

11. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats a) D = ¼  A (v bike ) 2 c) D = ¼  A (v bike + v air ) 2 b) D = ¼  A (v bike -v air ) 2 D = ¼  Av 2 where v is the speed of the object relative to the air The magnitude of the drag on a cyclist encountering a head wind is given by v air v bike Question 5 Solution

12. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats c) D = ¼  A (v bike + v air ) 2 b) D = ¼  A (v bike -v air ) 2 The magnitude of the drag on a cyclist encountering a tail wind is given by v bike v air a) D = ¼  A (v bike ) 2 Question 6

13. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Falling Cats a) D = ¼  A (v bike ) 2 c) D = ¼  A (v bike + v air ) 2 b) D = ¼  A (v bike -v air ) 2 D = ¼  Av 2 where v is the speed of the object relative to the air. ( Note: If v air > v obj, the drag force changes direction and the cyclist will be pushed by the wind.) The magnitude of the drag on a cyclist encountering a tail wind is given by v bike v air Question 6 Solution