Free Fall Powerpoint Presentation (Problems and Formulas)

Free Fall Powerpoint Presentation

1. Motion in One Dimension Free Fall

2. Free Fall Assumes no air resistance http://www.youtube.com/watch?v=5C5_dOEyAfk Acceleration is constant for the entire fall Acceleration due to gravity ( a g or g ) Has a value of - 9.8 m/s 2 (negative for downward) Roughly equivalent to -22 (mi/h)/s

3. What observations can you make about the picture?

4. Free Fall For a ball tossed upward, make predictions for the sign of the velocity and acceleration to complete the chart. Velocity (+, -, or zero) Acceleration (+, -, or zero) When halfway up When at the peak When halfway down + - zero - - -

5. Graphing Free Fall Based on your present understanding of free fall, sketch a velocity-time graph for a ball that is tossed upward (assuming no air resistance). Is it a straight line? If so, what is the slope? Compare your predictions to the graph to the right.

6. Remember Motion Graphs? x a t t Object is slowing down - acceleration + velocity Object is speeding up - acceleration - velocity v t

7. Stuntman Les Payne jumps off of a cliff and falls straight down into water 35 m below. What was his velocity when he hit the water? Practice 1 We have some things to think about: What sign will we need to use for his displacement if Les is moving downward? What sign will we need for the acceleration due to gravity? What is Les’ initial velocity?

8. Stuntman Les Payne jumps off of a cliff and falls straight down into water 35 m below. What was his velocity when he hit the water? Practice 1 G U E S S Δ x = -35 m a = - 9.81 m/s 2 v i = 0 m/s v f = ? v f 2 = v i 2 + 2a Δ x v f 2 = (0m/s) 2 + 2(-9.8m/s 2 )(-35m) -26 m/s Why did the answer end up being negative even though your calculator gave you a positive answer?

9. Justin Thyme drove his armored van through a guardrail on a bridge. After Justin escaped out the back, the van fell and hit the ground 1.1 4 s later. How high was the bridge? Practice 2

10. Practice 2 G U E S S t = 1.14 s a = -9.81 m/s 2 v i = 0 m/s Δx = ? Δ x = v i t + ½at 2 Δ x = (0m/s)(1.14s) + ½(-9.81m/s 2 )(1.14s) 2 6.37 m Why did the answer end up being negative? Is it necessary given the wording of the problem? Justin Thyme drove his armored van through a guardrail on a bridge. After Justin escaped out the back, the van fell and hit the ground 1.14 s later. How high was the bridge? Δ x =-6.37 m

11. Practice 3 You throw a watermelon straight up to your friend Bill Ding who is standing on a balcony 7.25 m above you. You throw the watermelon upward, it passes Bill, and then falls back down to him and hits the balcony. The entire journey took 1.95 s. How fast did you throw the watermelon? How high did the watermelon go?

12. You throw a watermelon straight up to your friend Bill Ding who is standing on a balcony 7.25 m above you. You throw the watermelon upward, it passes Bill, and then falls back down to him and hits the balcony. The entire journey took 1.95 s. How fast did you throw the watermelon? How high did the watermelon go? Practice 3 G U E S S Δ x = 7.25 m t = 1.95 s a = -9.81 m/s 2 v i = ? Δ x = v i t + ½at 2 7.25 m= (v i )(1.95s) + ½(-9.81m/s 2 )(1.95s) 2 13.3 m/s

13. You throw a watermelon straight up to your friend Bill Ding who is standing on a balcony 7.25 m above you. You throw the watermelon upward, it passes Bill, and then falls back down to him and hits the balcony. The entire journey took 1.95 s. How fast did you throw the watermelon? How high did the watermelon go? Practice 3 G U E S S v i = 13.3 m/s a = -9.81 m/s 2 v f = 0 m/s Δx = ? v f 2 = v i 2 + 2a Δ x (0m/s) 2 = (13.3m/s) 2 + 2(-9.81m/s 2 ) Δ x 9.02 m

14. Measurement Symbol Value acceleration due to gravity g 9.81 m/s 2 Freefall Summary

15. NOW YOU TRY Do practice F (1-3) from chapter 2 (page 64)