PHYS 210 Exam, Spring 2008

1. If the resultant force acting on a 2.0-kg object is equal to (3i + 4j) N, what is the change in kinetic energy as the object moves from (7i – 8j) m to (11i – 5j) m? a. +36 J b. +28 J c. +32 J d. +24 J This exam is to show you the style of questions you expect . 2. A 10-kg block on a horizontal frictionless surface is attached to a light spring (force constant = 1.2 kN/m). The block is initially at rest at its equilibrium position when a force (magnitude P) acting parallel to the surface is applied to the block, as shown. When the block is 8.0 cm from the equilibrium position, it has a speed of 0.80 m/s. How much work is done on the block by the force P as the block moves the 8.0 cm? a. 8.3 J b. 6.4 J c. 7.0 J d. 7.7 J e. 3.9 J 3. The horizontal surface on which the objects slide is frictionless. If F = 12 N, what is the tension in string 1, if M=2.0 kg? a. 35 N b. 30 N c. 40 N d. 45N 4. A 2.0-kg particle has an initial velocity of (5i – 4j) m/s. Some time later, its velocity is (7i + 3j) m/s. How much work was done by the resultant force during this time interval, assuming no energy is lost in the process? a. 17 J b. 49 J c. 19 J d. 53 J 5. A 2.0-kg block situated on a frictionless incline is connected to a light spring (k = 100 N/m), as shown. The block is released from rest when the spring is unstretched. The pulley is frictionless and has negligible mass. What is the speed of the block when it has moved 0.20 m down the plane? a. 76 cm/s b. 68 cm/s c. 60 cm/s d. 82 cm/s 37 6. A skier weighing 0.70 kN goes over a frictionless circular hill as shown. If the skier’s speed at point A is 9.2 m/s, what is his speed at the top of the hill (point B)? a. 3.1 m/s b. 6.2 m/s c. 5.2 m/s d. 4.1 m/s e. 6.5 m/s 7. The water level in a reservoir is maintained at a constant level. What is the exit velocity in an outlet pipe 3.0 m below the water surface? a. 2.4 m/s b. 3.0 m/s c. 5.4 m/s d. 7.7 m/s e. 49 m/s 8. A venturi tube may be used as the inlet to an automobile carburetor. If the 2.0-cm diameter pipe narrows to a 1.0-cm diameter, what is the pressure drop in the constricted section for an airflow of 3.0 cm/s in the 2.0-cm section? ( = 1.2 kg/m3.) a. 70 Pa b. 85 Pa c. 100 Pa d. 115 Pa e. 81 Pa Solutions: r F Wnet      1. Answer d) , where i f r r r       5. Answer c) sin 37 2 1 2 1 0 2 2 mgd kd mv    J v m v K W i f 17.04 4.6 6.7 ) ( 2 1 2 2 2 2       4. Answer: a) 2. Answer : c) 3. Answer: b) 6. c) cos45 ) 1( 2 1 2 1 2 2     mgR mv mv B A N Ma 12 6  and 1 3 3 T F Ma   7. d) gh v 2  8. e) Bernoulli + continuity equation