1 D motion: know your variables, position, displacement, velocity, speed acceleration, average and instantaneous.

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1 General: Typically, there will be multiple choice, short answer, and big problems. Multiple Choice and Short Answer On the multiple choice and short answer, explanations are typically not required (only if I explicitly say so). Explanations CAN get you partial credit. This is rare but possible. For example, you solve a multiple choice question correctly, with your work being legible and clear. Your work gives the answer 3m. However, you mark the answer 2m. In this case I might give you partial credit. However, I typically do not read hard to understand, incomplete or disorganized work. Some of the questions are conceptual, some quantitative. How many? Varies. Expect Big problems There will typically be 2 3 big problems. These will amount to 50 or more percent of the total exam points. Often it will be more cost effective to start with the big problems. Big problems are similar to what we do in class, homework or lab. I will often break big problems into parts. There are two examples at the end of this document. What to study Motion diagrams, how to make them, how to read them. What can I get out of it? Velocity? Acceleration? Speeding up, slowing down, direction changes? Can I find vectors qualitatively and quantitatively? Unit Conversion Significant figures 1 D motion: know your variables, position, displacement, velocity, speed acceleration, average and instantaneous. Know how to solve 1 D kinematics problems (just as we did in class and homework). Make sure to study x t, v t, and a t graphs, how do I get one from the other, how do they change if I change the coordinate system? Know how to add and subtract vectors graphically and analytically. Magnitude and direction as well as x and y components.

2 1) What is the sum of written with the correct number of significant figures? A) 8 B) 7.6 C) 7.62 D) E) ) Short answer: Convert 30 km/h to mm/s. Give your answer with two sig figs. Answer: mm / s 3. True / False: if an object is accelerating away from a point, it must be moving away from that point. a. True b. False 4. A particle moves with the position versus time graph shown. At which point in time is the particle moving with the slowest speed? Answer: 5. At a stoplight, a truck traveling at 15m/s passes a car as it starts from rest. The truck travels at constant velocity and the car accelerates at 3m/s 2. How many seconds will it take for the car to catch up to the truck? a. 5 b. 10 c. 15 d. 20 e An elevator is moving upward with constant acceleration. The dashed curve shows the position y of the ceiling of the elevator as a function of the time t. At the instant indicated by the dot, a bolt breaks loose and drops from the ceiling. Which curve best represents the position of the bolt as a function of time? Answer: Curve

3 7. 8. A car starts from point A, goes 50 km in a straight line to point B, immediately turns around, and returns to A. The time for this round trip is 2 hours. The magnitude of the average velocity of the car for this round trip is (in km/h): a. 0 b. 50 c. 100 d. 200 e. cannot be calculated without knowing the acceleration 9. A particle initially moving at 4m/s along the x axis is uniformly accelerated at 3 m/s 2 for 2 seconds and then coasts for 3 seconds. The total displacement after 5 seconds is Answer: m Answers: 1b x10 3 3b 4. I 5b 6. B 7c 8a 9. 44

4 Problem 1: (20 points) In all parts, briefly explain your work. A rocket is initially hovering (i.e. zero velocity) above the ground, at an altitude h. It reaches the ground in two phases: velocity Phase 1: It first falls freely through a distance of 180m (use g=10m/s 2 ). Phase 2: It then fires its engine which causes it to decelerate at a steady 6.0 m/s 2. It continues to slow down until it reaches the ground with a speed of 6 m/s. The figure shows a sketch of the velocity versus time graph. time a. [5 pts] Draw a sketch of the motion with important points, coordinate system, and all variables in it (just as we did in class). Make sure the direction of the y-axis is consistent with the v-t graph given. b. [4 pts] How long does phase 1 last and what is the rocket s velocity at the end of phase 1? c. [7 pts] How long is the rocket in the air and what was the initial altitude h?

5 d. [4 pts] Suppose a stone is right next to the rocket at time zero. It is tossed up into the air when the rocket starts to fall. What initial velocity must the stone have if it is to hit the ground at the same time as the rocket?

6 Problem 2: