Physics 201 Fall 2009 Exam 1 September 29, 2009

Transcription

1 Physics 201 Fall 2009 Exam 1 September 29, 2009 Acceleration due to earth s gravity g=9.8 m/s 2 Section # TA: 1. The density of seawater was measured to be 1.07 g/cm 3. This density in SI units is A) l kg/m 3 B) (1/1.07) 10 3 kg/m 3 C) kg D) kg E) kg/m 3 2. To convert a quantity from km/h to m/s, you must A) multiply by 1000 and divide by 60. B) multiply by 1000 and divide by C) multiply by 60 and divide by D) multiply by 3600 and divide by E) None of these is correct. 3. If x and t represent distance and time, respectively, the C in x = 1 /2Ct 2 must A) have the dimensions ML/T 2. B) have the dimensions M. C) have the dimensions L/T 2. D) have the dimensions L 2 /T 2. E) be dimensionless. 1

2 4. In Newton's Law of Gravity the universal gravitational constant G = Fr 2 /m 1 m 2, where F is the gravitational force between the two masses, m 1 and m 2, and r is the distance between them. What are the dimensions of G? A) L 2 M 1 T 2 B) L 3 M 1 T 2 C) L 2 M 2 T 2 D) L 3 M 1 T 2 E) L 3 M 1 T 3 5. The equation for the position of a train starting at x=0 as a function of time is given by x(t) = at 2 /2 + bt 3. The dimensions of b are: A) T -3 B) LT -3 C) LT -2 D) LT -1 E) L -1 T A car proceeding due south at 60 km/h makes a right turn, after which it is traveling due west at 80 km/h. What is its change in velocity? A) 100 km/h 37º north of west B) 100 km/h 37º south of west C) 20 km/h west D) 20 km/h 37º north of west E) 20 km/h 37º south of west 2

3 7. You drive for 30 min at 100 km/h and then stop for 15 min. You then drive for 45 min at 80 km/h. Your average speed for the entire trip is A) 73 km/h. B) 83 km/h. C) 88 km/h. D) 90 km/h. E) 97 km/h. 8. The graph shows the velocity of a particle as a function of time. In the 12 s shown, the particle travels A) 0 m. B) 1200 m. C) 640 m. D) 440 m. E) 200 m. 9. An airplane flies 600 miles with a tail wind in 2.0 hrs. If it takes 3.0 hrs to cover the same distance against the headwind, then what is the speed of the plane in still air? A) 270 mph B) 300 mph C) 240 mph D) 330 mph E) 250 mph 3

4 10. An object is moving in a straight line. At t = 0, its speed is 5.0 m/s. From t = 0 to t = 4.0 s, its acceleration is 2.5 m/s 2. From t = 4.0 s to t = 11.0 s, its speed is constant. The average speed over the entire time interval is A) 9.5 m/s B) 15 m/s C) 13 m/s D) 21 m/s E) 8.2 m/s 11. A projectile is fired vertically upward with a speed of 62 m/s. In the absence of air resistance, the maximum height the projectile attains is A) 25 km B) 98 m C) 200 m D) 19 km E) 3 m 12. Two of the graphs shown are INCORRECT for a particle undergoing onedimensional motion with constant acceleration. They are A) 1 and 2 B) 2 and 3 C) 3 and 4 D) 4 and 5 E) 1 and 5 4

5 13. A sandbag is released from a rising air balloon and hits the ground 7 seconds later. From what height was the sandbag dropped from if at the moment of release the balloon was traveling upward at 3 m/s. A) 219 m B) 240 m C) 459 m D) 261 m E) 55 m 14. A projectile is ejected from a 25-m high tower with a velocity of 40 m/s at an angle of 30 degrees to the horizontal first on Earth and then on Mars. What is the ratio of the time taken to hit the ground on Mars compared to Earth? (Assume g Mars = 0.38g Earth ) A) 2.3 B) 2.9 C) 0.38 D) 6.9 E) The relationship between the velocity of a body moving along the x axis and time is given by v = 2t 3 + 2t, where the units are SI units. The total distance the body travels between the times t = 2 s and t = 4 s is A) 132 m B) 144 m C) 136 m D) 120 m E) 156 m 5

6 16. The acceleration of a vehicle is given by a(t) = At where A is a constant. Its velocity as a function of time is (v o is a constant) A) B) v(t) = At 2 + v o C) v(t) = At + v o D) E) None of these is correct. 17. A particle has an initial velocity of 4.8 m/s toward the south and a final velocity of 7.1 m/s toward the east. The particle was subject to a constant acceleration for 0.25 s. The magnitude and the direction of the acceleration must have been A) 8.6 m/s 2 at 34.1º north of east B) 260 m/s 2 at 34.1º south of east C) 34 m/s 2 at 34.1º north of east D) 34 m/s 2 at 34.1º south of east E) 8.6 m/s 2 at 34.1º south of east 18. A pilot wants the heading of an airplane to be 45º east of north. The wind is from the west at 32 km/h, and the speed of the airplane through the air is 320 km/h. The pilot should maintain a heading of approximately A) 15º (measuring clockwise from north) B) 49º (measuring clockwise from north) C) 41º (measuring clockwise from north) D) 4º (measuring clockwise from north) E) 131º (measuring clockwise from north) 6

7 19. A skier leaves a ski jump with a horizontal velocity of 29.4 m/s. Ignoring air resistance, the instant before she lands three seconds later, her speed is: A) zero B) 29.4 m/s C) 41.6 m/s D) 50.9 m/s E) 88.2 m/s 20. A squirrel jumps from a tree limb onto a birdfeeder. The tree limb is 4.5 m above the ground and the top of the birdfeeder is 1.5 m above the ground. If the squirrel jumps horizontally with a velocity of 2.5 m/s then how far away in the horizontal direction can the bird feeder be for the squirrel to just make it onto the top of the feeder. A) 3.6 m B) 2.0 m C) 2.4 m D) 1.5 m E) 1.4 m 7