1. Warm-up Exercises: Watch this looped movie of an AirBurst TM rocket. What do you observe about the rocket’s motion from launch to (first) hitting the ground? What questions about the rocket’s motion can you ask? Discuss with your neighbors. Think About This: A motorcycle moving at constant speed 30 m/s on a straight road passes a stationary police car. At that instant, the police car begins to move with constant acceleration 3 m/s 2 in the same direction as the motorcycle. What questions about the motion in this situation can you ask? Discuss with your neighbors.

2. Tue. Apr. 5 – Physics Lecture #3 Motion in a Straight Line: 1-dimensional Kinematics 1.Announcements: meet in CAL West this afternoon and Wed. morning; I’m available over the lunch break today to discuss optics homework (meet in CAL West); info at web-site 2.Motion Concepts 3.Motion problems – graphically 4.Motion problems – algebraically 5.Free fall motion – motion under gravity

3. A motorcycle moving at constant speed 30 m/s on a straight road passes a stationary police car. At that instant, the police car begins to move with constant acceleration 3 m/s 2 in the same direction as the motorcycle. A motorcycle moving at constant speed 30 m/s on a straight road passes a stationary police car. What can we do with this?

4. Fig. 2.46Fig. 2.47

5. FIGURE 2.68 Consider the following graph of position vs. time: Hold up as many cards as needed. If none of these is a good answer, hold up the F card. a) During what time period(s) is the object moving in the positive direction? b) During what time period(s) is the object not moving? c) During what time period(s) does the object have negative speed? d) During what time period(s) does the object have negative velocity? Follow-ups: What is the average velocity of the object? What is the average speed of the object? Draw a velocity vs. time graph for the object.

6. A motorcycle moving at constant speed 30 m/s on a straight road passes a stationary police car. At that instant, the police car begins to move with constant acceleration 3 m/s 2 in the same direction as the motorcycle. Draw a position vs. time graph for the motorcycle. Draw a velocity vs. time graph for the motorcycle.

7. A motorcycle moving at constant speed 30 m/s on a straight road passes a stationary police car. At that instant, the police car begins to move with constant acceleration 3 m/s 2 in the same direction as the motorcycle. …a stationary police car. At that instant, the police car begins to move with constant acceleration 3 m/s 2 in the same direction as the motorcycle. What can we do with this?

9. Consider the velocity vs. time graph for a (world-class) runner, shown. a)Sketch the corresponding acceleration vs. time graph. b)How far did the runner move from 0 second to 10 seconds?

10. A race-car can go from rest to 30 m/s in 2 s. What is its (assumed constant) acceleration? Which of the following quantities do we know or can we assume from the problem statement? Hold up as many cards as appropriate. 1.  x = x – x 0 2. v 0 3. v = v f 4. a 5.  t = t – t 0 = t (assumes t 0 = 0) Which of the constant acceleration kinematics formulas would be most useful to answer the given question? Hold up as many cards as appropriate. 1. 2. 3.

11. A race-car can go from rest to 30 m/s in 2 s. a) What is its (assumed constant) acceleration? b) How far does it go in this time?

12. A motorcycle moving at constant speed 30 m/s on a straight road passes a stationary police car. At that instant, the police car begins to move with constant acceleration 3 m/s 2 in the same direction as the motorcycle. (notes: it’s slightly unrealistic to go from rest to 3 m/s 2 instantly, but we can assume that it happens over a short period of time; it’s also unrealistic to assume constant acceleration since the police car is likely to try to match the speed of the motorcycle instead of just catching up.) When and where does the police car catch up to the motorcycle? How fast is it going when that happens?

14. Given that the Air Burst ® rocket is in the air for about 4 s, what is the (approximate) initial speed of the rocket just after take-off (the launch speed of the rocket? Which of the following quantities do we know or can we assume from the problem statement? Hold up as many cards as appropriate. 1.  x = x – x 0 2. v 0 3. v = v f 4. a 5.  t = t – t 0 = t (assumes t 0 = 0) Which of the constant acceleration kinematics formulas would be most useful to answer the given question? Hold up as many cards as appropriate. 1. 2. 3.

15. Given that the Air Burst ® rocket is in the air for about 4 s, what is the (approximate) launch speed of the rocket? 1. 0 m/s 2. 10 m/s 3. 20 m/s 4. 40 m/s 5. 80 m/s 6. There isn’t enough information even to make an approximation What is the (approximate) maximum height that the rocket reaches?

16. A car moving at 20 m/s applies its brakes to reach a final speed of 10 m/s. The car moves 50 m while braking. Assume constant acceleration during braking. What questions about the car’s motion can be asked and answered?