1. Chapter 2 Kinematics in One Dimension Mechanics – forces & motion Kinematics – describes motion Dynamics – causes of motion (forces)

2. 2.1 – Displacement Displacement – straight-line distance b/w start & stop position.

3. 2.2 – Speed and Velocity Speed – scalar, Velocity - vector Instantaneous velocity … take calculus…

4. 2.3 – Acceleration Acceleration – a change in velocity; speeding up, slowing down or direction change.

5. Positive acceleration

6. Negative acceleration (deceleration)

7. ASSIGN: Ch. 2 #2-18 (evens) Page 52

8. A little about kinematics graphs… The independent variable is normally plotted on the x- axis and the dependent on the y-axis. Time is always the independent variable since it does not depend on anything. We can graph how distance traveled depends on time but not how time depends on distance traveled

9. Position vs. Time for NO Acceleration Slope = velocity Is this object accelerating? NO, constant slope on d vs. t graph

10. Positive and Negative Velocity

11. Position vs. Time for Acceleration

12. Velocity vs. Time Slope = acceleration Is this object accelerating? YES, constant slope on v vs. t graph

13. 2.6 – Freely Falling Bodies Freefall – when the only force acting on an object is gravity (downward). This picture does not represent freefall, why?

14. 2.6 – Freely Falling Bodies Neglecting air resistance, all objects fall at the same rate.

15. 2.6 – Freely Falling Bodies An object in freefall on earth has an acceleration equal to 9.8 m/s 2 (32 ft/s 2 ) g = -9.8 m/s 2 the acceleration due to gravity

16. 2.6 – Freely Falling Bodies g = -9.8 m/s 2 Time [sec]Acceleration (t) [m/s 2 ] Velocity (t) [m/s] Displacement (t) [m] 0 1 2 3 4 9.8 0 19.6 29.4 39.2 0 4.9 19.6 44.1 78.4

17. 2.4 – Kinematics Equations

18. 2.5 – Using Kinematics Equations Time [sec]Acceleration (t) [m/s 2 ] Velocity (t) [m/s] Displacement (t) [m] 0 1 2 3 4 9.8 0 19.6 29.4 39.2 0 4.9 19.6 44.1 78.4 Equations are meant to simplify problems, “don’t re-invent the wheel.”

19. 2.5 – Using Kinematics Equations Make a drawing of the situation Decide which directions are positive and negative. Write down the given variables In freefall, a = g = -9.8 m/s 2

20. ASSIGN: Ch. 2 #22-46 (every other even) Page 53

21. Chapter 2 Review Questions 1. Explain the difference between velocity and acceleration. 2.Two objects are thrown vertically into the air, first one and then, a bit later, the other. Is it possible for both objects to reach the same maximum height at the same time? 3.An object is dropped from rest. How fast is the object going after (a) 1 sec, (b) 2 sec, (c) 3.2 sec? 4. How far has the object dropped after (a) 1 sec, (b) 2 sec, (c) 3.2 sec?

22. Chapter 2 Review Questions 5. A person claims a hang time of 2 seconds. How high would this person jump if they really had this hang time? 6. A ball is thrown straight up into the air. (a) What is the acceleration of the ball during the entire time? (b) What is the velocity of the ball at the peak of its path? (c) If the ball was thrown up with an initial speed of 16.5 m/s, how long was the ball in the air? (d) How high did the ball reach?