5) A net force F is needed to give an object with mass m an acceleration a. If a net force of is applied to an object with mass 3m, what is the acceleration on this object? (A) 4a (B) a (C) 3a (D) 2a (E) 6a 6) A net force of 20 N is applied for 8 seconds to a 10-kg box initially at rest. What is the speed of the box at the end of the 8-second interval? (A) 160 m/s (B) 80 m/s (C) 2 m/s (D) 12 m/s (E) 16 m/s 7) A 5-kg block is pulled in the +x direction with acceleration a = 10 m/s2 by means of a force F. If the coefficient of kinetic friction between the block and the surface is MK = 0.5, what is the force F? (A) 15 N (B) 10 N (C) 25 N (D) 50 N (E) 75 N 8) A block of mass M is hung by ropes as shown. The system is in equilibrium. The point O represents the junction of the three ropes. Which of the following statements is true concerning the magnitudes of the three forces in equilibrium, given the data in the figure? ( A) F 1 = F2 = =F3 (B) F 1 = F2 > F3 (C) F , = F2 = F3 30 300 (D) F, = F2 = 2F, (E) F = F2 = =F3 M 9) A block of mass m is at rest on a rough inclined plane and is connected to another object with the same mass, hanging vertically as shown. The rope is assumed massless and the pulley is considered frictionless. The coefficient of static friction between the block and the plane is My. What is the magnitude of the static frictional force fs? (Hint: to figure out the direction of fy, determine in which direction the block would move in the absence of friction?) (A) mg(1 - sin 0) (B) mg(1 - cos () (Q mg(1 + sin0 ) (D) mg m (E) me(l - (and ) 1016) Julie carries an 8.0-kg suitcase as she walks 18 m along a horizontal walkway to her hotel room at a constant speed of 1.5 m/s. How much work does Julie do in carrying her suitcase? (A) 200 J. (B) 40 J. (C) 0J. (D) 300 J. (E) 2000 J 17) Which one of the following situations is an example of an object with a non-zero kinetic energy? (A) a drum of diesel fuel on a parked truck (B) a stationary pendulum (C) a boulder resting at the bottom of a cliff (D) a car parked at the top of a hill (E) a satellite in geosynchronous orbit 18) How much energy is dissipated in braking a 1500-kg car to a stop from an initial speed of 30 m/s? A) 24 KJ B) 675 kJ C) 280 KJ D) 820 kJ E) 12 KJ 19) The radii of two wheels are r, = 0.50 m and r2 = 0.20 m. If the same force is applied in the same direction to each wheel, what is the ratio 71/72 of the torques produced by this force on the two wheels? (A) 2.5 (B) 1.0 (C) 1.5 (D) 0.4 (E) 15 20) Consider the following four objects: a hoop, a flat disk, a solid sphere, and a hollow sphere. Each of the objects has mass M and radius R. The axis of rotation passes through the center of each object, and is perpendicular to the plane of the hoop and the plane of the flat disk. Which of these objects requires the largest torque to give it the same angular acceleration? (A) the solid sphere (B) the hollow sphere (C) the hoop (D) the flat disk (E) both the solid and the hollow spheresPHYS 207: FINAL EXAMINATION (20 questions) This is an open-book test. Write your NAME and ULID on the SCANTRON and test sheets. For each question, there is only one correct answer USE g = 10 m/s2 1) A car driving up an incline of angle @ at speed vo brakes hard and slides to a complete stop over distance d. If the same car brakes hard while driving down the same incline with initial speed vo, the stopping distance is d2. What is the relation between the stopping distances d, and d2? (A) d, > d2 (B) d,