1. Falling Objects 2.3 pp. 60-65 Mr. Richter

2. Agenda  Warm-Up  Review HW p. 58 #4-6  Questions about the Lab?  Intro to Free Fall  Notes:  Free Fall  Velocity During Free Fall  Acceleration During Free Fall  Problem Solving w/ Free Fall

3. Objectives: We Will Be Able To…  Relate the motion of an object in free fall to motion with constant acceleration.  Calculate displacement, velocity, and time at various points in the motion of an object in free fall.  Compare the motions of different objects in free fall.

4. Warm-Up:  Mr. Richter throws his green ball up in the air and then catches it.  Sketch the Position vs. Time Graph and Velocity vs. Time Graph of the motion of the ball.

5. Free Fall

6.  If a piece of paper and a ball bearing are dropped from the same place, will they fall at the same rate? Why or why not?  Discuss at your table and we will discuss as a class in a minute.

7. Free Fall  Objects dropped near the surface of a planet fall at the same rate.  REGARDLESS OF MASS!  This is only true in the absence of air resistance (friction). In a vacuum.

8. Free Fall

9.  In the picture, the distance the objects fall each instant is increasing.  So the objects must be accelerating.  This is the acceleration due to gravity.  On Earth, g = 9.81 m/s 2

10. Velocity and Acceleration in Free Fall

11.  Once something is released (thrown, dropped, etc.), it immediately starts experiencing the acceleration due to gravity.  Any positive initial velocity is starting to diminish.  Once there is no more positive velocity, the velocity of the object becomes increasingly negative.

12. Velocity and Acceleration in Free Fall  Consider a ball thrown upward with an initial velocity of +19. 62 m/s Time (sec)Velocity (m/s) 019.62 19.81 20 3-9.81 4-19.62

13. Velocity and Acceleration in Free Fall  Objects with initial positive velocity in free fall have VvT graphs that look something like this:

14. Velocity and Acceleration in Free Fall  Important concepts that play a role in problem solving:  If an object is propelled upward, v = 0 at the object’s highest point (peak).  If an object is propelled from and returned to the same point:  its time to reach its peak is exactly half the time it takes to complete the round trip.  v 1 = - v f (initial and final speeds are equal and opposite)  Δ y = 0

15. Problem Solving with Free Fall

16. Problem Solving  All of the formulas on p. 58 still apply, with two minor changes:  Δ y instead of Δ x (y-axis goes up and down)  Acceleration a is almost always –g = -9.81 m/s 2

17. Practice Problem (2 steps)  Jason hits a volleyball so that it moves with an initial velocity of 6.0 m/s straight upward. If the volleyball starts from 2.0 m above the floor, how long will it be in the air before it strikes the floor?

18. Wrap-Up: Did we meet our objectives?  Relate the motion of an object in free fall to motion with constant acceleration.  Calculate displacement, velocity, and time at various points in the motion of an object in free fall.  Compare the motions of different objects in free fall.

19. Homework  p 65 #1-6 Due Monday