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RIII-1. An elevator is going up at a constant speed. Near the top floor, it starts to slow to a stop. During the period that it is slowing down, its acceleration is A) downward. B) upward. C) in some other direction. RIII-2. Consider the vectors V1 and V2 shown. What is the direction of V = V2 – V1 V1 + V = V2 v1 direction of v? D v2 C A B RIII-3. Consider the vector A Which equation is correct? A) Ax = +A cos B) Ax = –A cos C) Ax = +A sin D) Ax = –A sin y A x RIII-4. A projectile is fired at an initial speed of vo at an angle of above the horizontal. Which of the following expressions could possibly be the correct expression for the range of the projectile? (Hint) check the units). A) x 2g v0 tan vo2 C) x sin 2 g B) x 2g 2 vo sin(2) D) x g sin 2 2 vo RIII-5. A plane in horizontal flight moving at constant velocity drops a heavy package while approaching the border of a kingdom. Which crosses the border first? (As usual, assume that air resistance is negligible.) A) the plane B) the package C) both cross at the same instant v = constant border RIII-6. A boy of mass M = 50 kg pushes on a baby carriage of mass M/5 = 10 kg. The force on the carriage from the boy has magnitude FonCarriage. The force on the boy from the carriage handle has magnitude FonBoy. How do the forces compare? A) FonCarriage = 5 FonBoy C) FonCarriage = FonBoy B) FonCarriage = 0.2 FonBoy RIII-7. A heavy–duty truck pulling a light trailer is accelerating forward. How does the force on the truck FonTruck from the trailer compare to the force on the trailer FonTrailer from the truck? a A) FonTruck > FonTrailer C) FonTrailer = FonTruck B) FonTrailer > FonTruck RIII-8. In the 1600's, Otto Van Güricke, a physicist in Magdeburg, fitted two hollow bronze hemispheres together and removed the air from the resulting sphere with a pump. Two eight-horse teams could not pull the spheres apart, even though the hemispheres fell apart when air was re-admitted. Suppose von Güricke had tied both teams of horses to one side and bolted the other side to a heavy tree trunk. In this case the tension in the rope would be... A) twice B) exactly the same as C) half what it was before. RIII-9. A box of mass m is sitting at rest on a horizontal table. The magnitudes of the normal force N and the weight mg are equal: N = mg. True(A) or false(B): The forces N and mg are a Newton's Third Law action–reaction pair. RIII-10. A crate of mass m rests on a rough surface with coefficient of kinetic friction K. A horizontal force F is applied which maintains a constant acceleration a. What is the size of that force? a m A) F = ma + mg C) ma E) None of these. F B) F = ma – mg D) (ma + mg)/ RIII-11. A crate of mass m is accelerated to the left with a string at an angle q above the horizontal. The coefficient of kinetic friction is K. The coordinate system has been chosen as shown. What is the correct y–equation? y F x a K A) F N mg 0 C) Fsin N mg 0 E) None of these B) Fcos K N ma D) Fcos N mg 0 RIII-12. A stationary crate is pulled to the left with a horizontal cord. The tension in the cord is T and the crate is not moving. The coefficient of state friction is S. Which of the following statements must be true? T S I. The magnitude of the force of friction is T. II. The magnitude of the force of friction is SN. III.The magnitude of the force of friction is Smg. A) All 3 statements must be true. B) All 3 statements are not necessarily true. C) Only 1 of the 3 statements must be true. D) Only 2 of the 3 statements must be true. RIII-13. Consider the two equations in two unknowns x and y) 3x – y = 0 What is x? A) 2 B) 3 x+y= 2 C) 1/4 D) 4 E) None of these RIII-14. A rider in a "barrel of fun" finds herself stuck with her back to the wall. The free-body diagram is shown. Is the following statement definitely true for this situation? sN=mg A) Yes, it is certainly true. B) No, it might not be true. RIII-15. The free-body diagram for a car rounding a banked curve is shown. The car is going so fast that it is about to slip. The coordinate system has been chosen. y a N x SN mg What is the correct y-equation? A) N sin + sN cos – mg = 0 B) N – sN sin – mg cos = 0 C) N – mg cos = 0 E) None of these D) N cos – sN sin – mg = 0 RIII-16. What is the magnitude of the force of gravity exerted on the Earth by an apple that is falling from a tree to the ground? A) mg B) > mg C) < mg m RIII-17. For a small mass m on the surface of a planet of mass M GMm = mg ? and radius R, is it always true that R2 A) Yes, this is always true regardless of whether the mass m is in free-fall or not. B) No, this is not always true. RIII-18. Astronaut Dave Bowman accidentally drops his coffee cup while eating breakfast inside the rotating centrifuge of the spacecraft Discovery. What happens to the coffee cup? A) the cup hangs in space before Bowman's face. B) the cup accelerates toward the floor and smashes into little bits. C) the cup travels in a straight line at constant speed until hitting something and smashing into little bits. RIII-19. Recall that Kepler's 2nd law says that planets move faster when closer to the Sun. (KII: A line drawn from the sun to the planet sweeps out equal areas in equal times). A small planet of mass m is in elliptical orbit about a large star of mass M. Which of the following statements is always true as the planet orbits the star? m M 1. The direction of the acceleration of the planet is toward the star. 2. The magnitude of the acceleration of the planet is a = v2/r ,where v is the speed of the planet and r is the distance between the planet and the star. 3. The magnitude of the force between the planet and the star is constant. 4. The speed of the planet is constant. A) All are true always. B) None are true always. C) Only 1 and 2 are true always. D) Only 1 is true always. E) Some other combination.