1. Think – Pair - Share
1. A 1-pound block and a 100-pound block are placed side by side at the top of a frictionless hill. Each is given a very light tap to begin their race to the bottom of the hill. In the absence of air resistance
the 1-pound block wins the race.
the 100-pound block wins the race.
the two blocks end in a tie.
there’s not enough information to determine which block wins the race.

2. A 1-pound block and a 100-pound block are placed side by side at the top of a frictionless hill. Each is given a very light tap to begin their race to the bottom of the hill. In the absence of air resistance
the 1-pound block wins the race.
the 100-pound block wins the race.
the two blocks end in a tie.
there’s not enough information to determine which block wins the race.
IG2.4

3. Position-Versus-Time
Trucker Bob starts the day 120 miles west of Denver. He drives east for 3 hours at a steady 60 miles/hour before stopping for his coffee break.
Draw a position-versus-time graph for Bob, including appropriate numerical scales along both axes.
Let Denver be located at x = 0 and assume that the x-axis points to the east.

4. Uniform Motion
Straight-line motion in which equal displacements occur during any successive equal-time intervals is called uniform motion. For one-dimensional motion, average velocity is given by
Notice the symbol Δ.
It represents a displacement and an interval in time - not position or instant in time

5. Problem Solving Strategy
Sally opens her parachute at an altitude of 1500 m. She then descends slowly to earth at a steady speed of 5 m/s. How long does it take her to touch down?
Draw pictorial representation – coordinates, symbols
Motion diagram
Mathematical Representation
Are results reasonable?

6. Acceleration Average Acceleration Instantaneous Acceleration
The time rate of change of velocity
Change in velocity divided by change in time
The as at a specific instant of time t is given by the derivative of the velocity

9. Trajectory of a ball
Turning point – What is the acceleration as the ball rises, drops, at the top?

10. Tactics: Interpreting graphical representations of motion

11. Motion with Constant Acceleration

12. Finding Velocity from the Acceleration
If we know the initial velocity, vis, and the instantaneous acceleration, as, as a function of time, t, then the final velocity is given by
Or, graphically,

13. EXAMPLE 2.21 Finding velocity from acceleration
QUESTION:

14. EXAMPLE 2.21 Finding velocity from acceleration

15. Problem-Solving Strategy: Kinematics with constant acceleration

16. Example 1
Bob throws a ball straight up at 20 m/s, releasing the ball 1.5 m above the ground. What is the maximum height of the ball? What is the ball’s impact speed as it hits the ground?

17. Example 2
A sprinter accelerates at 2.5 (m/s)/s until reaching his top speed of 15 m/s. He then continues to run at top speed. How long does it take him to run the 100-m dash?
(It’s worth including a graphical analysis with this problem.)

18. Kinematic Curves

19. Upcoming Assignments MasteringPhysics online HW due tonight by 11 pm
Pre-class MasteringPhysics assignment due before class on Tuesday
Pre-class MasteringPhysics assignment due before class on Thursday
MasteringPhysics online HW due Thursday by 11 pm