Phys 111 Exam 1 September 19, You cannot use CELL PHONES, ipad, IPOD... Good Luck!!! Name Section University ID

Transcription

1 Phys 111 Exam 1 September 19, 2017 Name Section University ID Please fill in your computer answer sheet as follows: 1) In the NAME grid, fill in your last name, leave one blank space, then your first name. 2) Write your ID number in the IDENTIFICATION NUMBER section of the sheet. 3) Write your recitation section number in the spaces K, L in the SPECIAL CODES section. Single digits should be preceded by a 0 (e.g. section 1 is written as 01). 4) Fill in the circles on the sheet corresponding to the letters or numbers of your name, ID and section with a #2 pencil. Note (a) Use g = 9.81 m/s 2 if needed. (b) There are 20 multiple choice problems. (c) 2.0 hour Exam (no one can leave before 9:15 PM). (d) Formula sheets are available (attached at the last two pages). (e) Record sheet is attached after the 20 exam problems. You cannot use CELL PHONES, ipad, IPOD... Good Luck!!! 1

2 1. Which of the following is a vector and not a scalar? (1) Wind blowing N/NW at 20 mph (2) A temperature of 90º Fahrenheit (3) A mass of 200 kg (4) A block moving with a speed of 3 m/s at 30º above the floor (A) 1 and 2 (B) 1 and 3 (C) 2 and 4 (D) 1 and 4 (E) None of them 2. Velocity (v) is related to acceleration (a) and distance (d) by the following expression: v 2 = 2ax p. What is the power p that makes this equation dimensionally consistent. (A) p = -2 (B) p = -1 (C) p = 0 (D) p = 1 (E) p = 2 3. You drive 4 miles at 30 mi/hr and then another 4 miles at 50 mi/hr. What is your average speed for the whole 8-mile trip? (A) greater than 40 mi/hr. (B) equal to 40 mi/hr. (C) less than 40 mi/hr. (D) equal to 40 km/hr. (E) Not possible to determine from the information given. 4. A car is traveling with a constant speed when the driver suddenly applies the brakes, causing the car to slow down with a constant acceleration of magnitude 3.50 m/s2. If the car comes to a stop in a distance of 30.0 m, what was the car's original speed? (A) 10.2 m/s (B) 14.5 m/s (C) 105 m/s (D) 210 m/s (E) 315 m/s 5. The right figure shows a graph of the velocity of an object as a function of time. What is the displacement of the object from 0 s to 6.0 s? (A) 0 m (B) 20 m (C) 40 m (D) 60 m (E) 80 m 2

3 6. A car traveling with velocity v is decelerated by a constant acceleration of magnitude a. It travels a distance d before coming to rest. If its initial velocity were increased by a factor of two, the distance required to stop would (A) increase by a factor of two. (B) decrease by a factor of two. (C) stay the same. (D) increase by a factor of four. (E) decrease by a factor of four. 7. Consider two vectors and shown in the figure below. The difference - is best illustrated by (A) choice (a). (B) choice (b). (C) choice (c). (D) choice (d). 8. A plane moving 200 m/s horizontally fires a projectile with speed 50 m/s in a forward direction 30.0 below the horizontal. At that instant, what is the speed of the projectile with respect to a stationary observer on the ground? (A) 245 m/s (B) 250 m/s (C) 268 m/s (D) 293 m/s (E) 308 m/s 9. A stone is thrown horizontally with an initial speed of 10 m/s from the edge of a cliff. A stopwatch measures the stone's trajectory time from the top of the cliff to the bottom to be 4.3 s. What is the height of the cliff if air resistance is negligibly small? (A) 22 m (B) 43 m (C) 77 m (D) 91 m 3

4 10. A boy throws a ball with an initial velocity of 25 m/s at an angle of 30 above the horizontal. If air resistance is negligible, how high above the projection point is the ball after 2.0 s? (A) 5.4 m (B) 13 m (C) 25 m (D) 43 m (E) 50 m 11. A 450-kg sports car accelerates from rest to 100 km/h in 4.80 s. What magnitude force does a 68.0 kg passenger experience during the acceleration? (A) 394 N (B) 82.0 N (C) 342 N (D) 311 N (E) 0 N 12. A 45.0-kg person steps on a scale in an elevator. The scale reads 460 N. What is the magnitude of the acceleration of the elevator? (A) 4.91 m/s2 (B) 9.81 m/s2 (C) 46.9 m/s2 (D) m/s2 (E) m/s2 13. A 1200-kg car is pulling a 500-kg trailer along level ground. Friction of the road on the trailer is negligible. The car accelerates with an acceleration of 1.3 m/s2. What is the force exerted by the car on the trailer? (A) 550 N (B) 600 N (C) 650 N (D) 700 N (E) 750 N 14. A 50.0-kg box is being pushed along a horizontal surface. The coefficient of kinetic friction between the box and the ground is What horizontal force must be exerted on the box for it to accelerate at 1.20 m/s 2? (A) 232 N (B) 60.0 N (C) 491 N (D) 116 N (E) 172 N 4

5 15. Two forces act on a object. One force has magnitude 65 N directed 59 clockwise from the positive x-axis, and the other has a magnitude 35 N at 32 clockwise from the positive y-axis. What is the magnitude of this object's acceleration? (A) 0.9 m/s2 (B) 1.1 m/s2 (C) 1.3 m/s2 (D) 1.5 m/s2 (E) 1.7 m/s2 16. The figure shows a block of mass M hanging at rest. The light wire fastened to the wall is horizontal and has a tension of 38 N. The wire fastened to the ceiling is also very light, has a tension of and makes an angle θ with the ceiling. Find the angle θ. (A) 50 (B) 40 (C) 33 (D) 65 (E) A horizontal 52-N force is needed to slide a box across a flat surface at a constant velocity of 3.5 m/s. What is the coefficient of kinetic friction between the box and the floor? (A) 0.09 (B) 0.11 (C) 0.12 (D) 0.13 (E) A box of mass m 1 = 10.0 kg rests in smooth, horizontal floor next to a box of mass m 2 = 5.00 kg. If you push on the box 2 with a horizontal force of magnitude of F = 20.0 N. What is the magnitude of the contact force between the boxes? (A) 0.0 N (B) 5.53 N (C) 6.67 N (D) 20.0 N (E) 13.3 N 5

6 19. Pulling up on a rope, you lift a 7.27-kg bucket of water from a wall with an acceleration of 1.24 m/s 2. What is the tension of the rope? (A) 62.3 N (B) 71.3 N (C) 80.3 N (D) 89.3 N (E) 98.3 N 20. An object attached to a spring is pulled across a horizontal frictionless surface. If the force constant (spring constant) of the spring is 45 N/m and the spring is stretched by 0.88 m when the object is accelerating at what is the mass of the object? (A) 36 kg (B) 31 kg (C) 24 kg (D) 28 kg (E) 12 kg 6

7 Record Sheet of Exam 1, Physics 111, Fall 2017 You may fill in this sheet with your choices and take it with you for comparison to the posted answers

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