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EASTERN MEDITERRANEAN UNIVERSITY - Department of Physics PHYS 101 –MIDTERM EXAM 2008-09 SUMMER SCHOOL (August 05, 2009) STUDENT NO NAME SURNAME BOOKLET A INSTRUCTIONS Answer all the questions. o Section I consists of 15 multiple choice questions. Each question is worth 1 point. Mark the correct answers on the ANSWER GRID below, by encircling the appropriate letter. o Section II consists of 3 problems worth a total of 15 points. Write your answers directly on the page of each problem. For full credit, fully justify your answers. Time allowed for the exam is 120 minutes. You may NOT use books, notes, dictionaries, formula sheets, PDAs, mobile phones, etc. You may use a calculator. CONSTANTS AND USEFUL FORMULAS Constants g = 9.80 m/s2 G 6.67 10 11 2 Nm / kg Velocity and acceleration: dr (t ) dv (t ) v(t ) , a(t ) dt dt Radial or centripetal acceleration: 2 Constant acceleration kinematic equations: 1 v(t ) vo at , r (t ) ro v ot at 2 2 v2 aR ac r Newton’s law of universal gravitation: mM F G 2 , r Newton’s second law: Mass of the Earth= 5.9742 × 1024 kg Mass of the Moon = 7.36 × 1022 kg Wnet K 2 K1 1 K mv2 2 F ma The average centre-to-centre distance from the Earth to the Moon is 384,403 km ANSWER GRID Mark your answers to the test questions on this grid by PLACING A CIRCLE around the letter of your choice. Force of friction: Ffr Fk k FN (kinetic) Ffr Fs s FN (static) W F d 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 a a a a a a a a a a a a a a a b b b b b b b b b b b b b b b c c c c c c c c c c c c c c c d d d d d d d d d d d d d d d e e e e e e e e e e e e e e e This line for instructor use only Section I For (15 points) instructor use only Problem 1 ( 5 points) Section II (15 points) Problem 2 Problem 3 (5 points) (5 points) TOTAL PHYS101 Midterm Examination Summer 2008-09 1. You drive for 30 seconds at 30 m/s and then for another 30 seconds at 50 m/s. What is your average speed for the whole trip? a) b) c) d) e) x (m ) 40 m/s 35 m/s 45 m/s 20 m/s 60 m/s t a) b) c) d) 2. You run 20 meters at 10 m/s and then walk 40 meters at 5 m/s. What is your average speed for the whole 60 meters? a) b) c) d) e) v>0, a>0 v>0, a<0 v<0, a>0 v<0, a<0 7. For a cannon on Earth, the cannonball would follow path (b). If the cannon was fired on Moon where gMoon = 0.3gEarth, which path would the cannonball take in the same situation? 7.5 m/s 15.0 m/s 6.0 m/s 8.0 m/s 10.0 m/s a) 3. If the average velocity is non-zero over some time interval, does this mean that the instantaneous velocity is never zero during the same interval? a) b) c) d) a) b) c) d) e) they are perpendicular to each other they are parallel and in the same direction they are parallel but in the opposite direction they are at 45° to each other they can be at any angle to each other 9. You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will? Alice’s ball it depends on how hard the ball was thrown neither - they both have the same acceleration Bill’s ball a) b) c) d) 5. You drop a rock off a bridge. When the rock has fallen 4 m, you drop a second rock. As the two rocks continue to fall, what happens to their separation? a) b) c) d) d) 8. Given that A + B = C, and that lAl + lBl = lCl , how are vectors A and B oriented with respect to each other? yes no it depends Impossible to tell 4. Alice and Bill are at the top of a building. Alice throws her ball downward. Bill simply drops his ball. Which ball has the greater acceleration just after release? a) b) c) d) c) b) quickly lag behind the plane while falling remain vertically under the plane while falling move ahead of the plane while falling not fall at all 10. A projectile is launched from the ground at an angle of 30 . At what point in its trajectory does this projectile have the least speed? the separation increases as they fall the separation stays constant at 4 m the separation decreases as they fall it is impossible to answer without more information e) f) g) h) i) 6. The graph of position versus time for a car is given below. Which of the following statements about the acceleration and velocity of the car is correct? just after it is launched at the highest point in its flight just before it hits the ground halfway between the ground and the highest point speed is always constant 11. From rest, we step on the gas of our Ferrari, providing a force F for 4 seconds, speeding it up to a final speed 2 PHYS101 Midterm Examination v. If the applied force were only 1/2 F, how long would it have to be applied to reach the same final speed? e) both the same (N = 0) 14. If you push with force F on either the heavy box ( M2) or the light box (M1), in which of the two cases below is the contact force between the two boxes larger? a) 16 s b) 8 s c) 4 s d) 2 s e) 1 s 12. A block of mass m rests on the floor of an elevator that is accelerating upward. What is the relationship between the force due to gravity and the normal force on the block? f) g) h) i) j) a) If we push M1 b) If we push M2 c) both are the same M1 F F M2 1 1 2 15. Two blocks of masses 2m and m are in contact on a horizontal frictionless surface. If a force F is applied to mass 2m, what is the force on mass m ? N > mg N = mg N < mg (but not zero) N = 0 depends on the size of the elevator A A B both the same (N = mg) both the same (0 < N < mg) M2 M1 1 F 13. Consider two identical blocks, one resting on a flat surface and the other resting on an incline. For which case is the normal force greater? a) b) c) d) Summer 2008-09 a) b) c) d) e) B 2m m 2F F 1/2 F 1/3 F 1/4 F SECTION II Problem 1 (total of 5 points) Box A, of mass mA=10 kg, is placed on a surface inclined at 37° to the horizontal. It is connected by a lightweight cord, which passes over a massless and frictionless pulley, to a second box B, which hangs freely as shown. If the coefficient of kinetic friction is 0.20 and mB=20 kg: a) Plot the free body diagrams for mA and mB separately. (2 points) b) If mA moves to the left find the acceleration of the system? (3 point) 3 PHYS101 Midterm Examination Problem 2 (total of 5 points) Use the information given on the cover page to calculate at what speed does the moon orbit the earth? Problem 3 (total of 5 points) A car traveling 60 km/h can brake to a stop within a distance d of 20 m. If the car is going twice as fast, 120 km/h, what is its stopping distance? Assume the maximum braking force is approximately independent of speed. 4 Summer 2008-09