<p>September 8, 2009 PHY 2048 Fall ‘09 Conceptual Review: Chapter 2.7-3.8</p><p>A . 1D Motion w/ Constant Acceleration 1. A car is moving in a straight line with a constant speed. You know the initial velocity and final velocity of the motion. What is the easiest way to find the displacement? </p><p>2. A car traveling at a constant speed of 20 m/s passes a trooper. One second later, the trooper sets off in chase with a constant acceleration of 4 m/s2. How long does it take the trooper to overtake the car? </p><p>B. Free Fall 1. A projectile is moving in the vertical direction. What is the velocity at the top of the motion? </p><p>2. A stone is thrown upward from the ground level with an initial velocity of 20 m/s. What is the velocity of the stone when it hits the ground? </p><p>3. Two balls are thrown from the top of a building. One is upward and the other one is downward with the same initial speed. Which one is faster when they hit the ground?</p><p>B. Vectors 1. Can the sum of two vectors have a magnitude equal to the magnitude of the sum of the two vectors? What about the difference of two vectors? </p><p>2. If a·b = a·c, then b = c?</p><p>3. If a vector has components (x, y) = (-2, 1), then what is the direction of the vector? </p><p>4. Two vectors are expressed in components (ax, ay) and (bx, by). What is the angle between the two vectors? September 8, 2009 PHY 2048 Discussion – Fall ‘09 Practice Exam Problems (Chapter 2.7-3.8)</p><p>1. The acceleration of an object, starting from rest, is shown in the graph below. Other than at t = 0, when is the velocity of the object equal to zero? (Acceleration vs. Time Graph) a. During the time interval from 1.0 s to 3.0 s b. At t = 3.5 s c. At t = 4.0 s d. At t = 5.0 s e. At no other time less than or equal to 5 s. </p><p>2. At a stop light, a truck traveling at 15 m/s passes a car as it starts from rest. The truck travels at a constant velocity and the car accelerates at 3 m/s2. How much time does the ca take to catch up to the truck? (Motion w/ Constant Acceleration) a. 5s b. 10 s c. 15s d. 20s e. 25s</p><p>3. At time t = 0 a car has a velocity of 16 m/s. It slows down with an acceleration given by -0.50t, in m/s 2 for t in seconds. By the time it stops it has traveled: (Motion w/ Linear Acceleration) a. 15 m b. 31 m c. 62 m e. 85 m e. 100 m</p><p>4. An object is thrown vertically upward with a certain initial velocity in a world where the acceleration due to gravity is 19.6 m/s2. The height to which it rises is ____ that to which the object would rise if thrown upward with the same initial velocity on Earth. Neglect friction. (Free Fall) a. half b. √2 times c. twice d. four times e. cannot be calculated from the given data</p><p>5. In the diagram, A has magnitude 12 m and B has magnitude 8 m. The x component of A+B is about (Addition of Vectors) a. 5.5 m b. 7.6 m c. 12 m d. 14 m e. 15 m </p><p>6. Let S = (1m)i+(2m)j+(2m)k and T = (3m)i+(4m)k. The angle between these two vectors is given by: (Scalar Product) a. cos-1(14/15) b. cos-1(11/225) c. cos-1(104/225) d. cos-1(11/15) e. cannot be found since S and T do not lie in the same plane. </p><p>7. Two vectors lie with their tails at the same point. When the angle between them is increased by 20º the magnitude of their vector product doubles. The original angle between them was about: (Vector Product) a. 0 b. 18º c. 25º d. 45º e. 90º</p><p>Answers: 1-e 2-b 3-d 4-a 5-c 6- d 7-b</p>