Physics 23 Exam 1 Spring 2009 Dr. Alward Page 1

Transcription

1 Physics 23 Exam 1 Spring 2009 Dr. Alward Page 1 1. An arrow is fired upward at a speed of 100 m/s. What will be its height (in meters) one second before it reaches its maximum height? A) 505 B) 496 C) 398 D) At about what upward speed (in m/s) must a bullet leave a pistol if it is to rise to a maximum height of 1400 meters? A) 102 B) 108 C) 124 D) The apparent weight of an object accelerating upward in an elevator at 5.6 m/s 2 is 150 N. What is the object's mass, in kg? A) 4.78 B) 6.54 C) 9.12 D) An automobile travels at an average speed of 45 mph for 20 minutes, then at a speed of 27 m/s for half an hour. What was the automobile's average speed (in m/s) during this entire period? A) 36 B) 31 C) 24 D) 26 Page 1

2 Physics 23 Exam 1 Spring 2009 Dr. Alward Page 2 5. Three forces, A, B, and C lie in a plane, pulling on an object. Force A has magnitude of 200 N, and makes an angle of 240 o with respect to the positive x axis. Force B has a magnitude of 140 N, and points in the negative x direction. Force C makes an angle of -45 o (45 degrees below the positive x-axis), and has a magnitude of 400 N. What is the sum (in N) of the three forces? (Solve either by estimating with the graphical method, or use the more precise component method.) A) 5 B) 110 C) 260 D) 460 E) A force of 300 N begins pushing on a 150 kg block initially at rest on a horizontal, frictionless surface. The pushing force is directed at angle of 40 o below the horizontal. What will be the speed (in m/s) of the block after it has moved 120 meters? A) 8 B) 12 C) 15 D) An object is fired at 65 m/s from the top of a 40-m tall cliff at an angle of 15 o below the horizontal. How far (in m) from the base of the cliff will the object land? (Answers are rounded to the nearest 1 meter.) A) 102 B) 146 C) 184 D) A flag pole is 12.3 meters tall, and is 40 meters from the base of a tall building. A 70 meter long wire is connected between the top of the building and the top of the flag pole. What angle (in degrees) does the wire make with respect to the buildling? A) 35 B) 55 C) 40 D) 30 Page 2

3 Physics 23 Exam 1 Spring 2009 Dr. Alward Page 3 9. A rock is thrown straight upward from the top of a building that is 50 meters tall. It strikes the ground below with a speed of 40 m/s. At what about speed (in m/s) was the rock thrown? A) 20 B) 25 C) 30 D) An arrow is fired over level ground at a speed of 35 m/s and at an angle of 70 o above the horizontal. What will be its speed (in m/s) 3.0 seconds later? A) 46 B) 35 C) 21 D) An 4-kg object accelerates from rest under the action of a force whose x- and y-components are 40 N, and 60 N, respectively. What will be the object's speed (in m/s) three seconds later? A) 49 B) 54 C) 59 D) Two point-sized objects of identical mass are separated by 500 m. What would have to be the mass (in kg) of each object in order that the force that one object exerts on the other is 100 N? (G = 6.67 x N-m 2 /kg 2.) A) 5.96 x 10 8 B) 6.46 x 10 8 C) 7.50 x 10 7 D) 4.64 x 10 9 Page 3

4 Physics 23 Exam 1 Spring 2009 Dr. Alward Page The gravitation force between two point-sized objects is 240 nn (nano-newtons). If the distance between them is reduced to one-third of the initial separation, and one of the objects is replaced by an object with one-half the mass, while the other object is replaced by an object that's one-sixth the mass, the force between the new pair of objects will be (in nn): A) the same B) 180 C) 210 D) Two cars leave an intersection. Car A is traveling east at 30 m/s, while Car B is traveling north at 20 m/s. What is the heading (in degrees) of Car A, according to Car B? (Note: heading is measured relative to north, clockwise.) A) 236 B) 334 C) 124 D) The position of an object moving along the x-axis is a function of time: x(t) = 5 + 3t 2 + 2te t, where x is in meters, and t is in seconds. At what time t (in seconds) will the object be at x = 40 m? A) 2.3 B) 2.1 C) 1.7 D) A football is kicked at speed 30 m/s at an angle of 25 o over level ground. How long (in s) will it take the ball to fall to ground after reaching its maximum height? A) 1.76 B) 1.98 C) 2.13 D) 2.56 Page 4

5 Physics 23 Exam 1 Spring 2009 Dr. Alward Page A ball rolls over a table top that is 1.8 meters high. It lands 0.8 meters from the table. What was the speed (in m/s) of the ball before it left the table? A) 1.0 B) 1.3 C) 1.7 D) An object moving at constant velocity travels from x = -19 m to x = 43 m in 7.5 seconds. After how many more seconds will the object be at x =86 m? A) 15.0 B) 5.2 C) 9.8 D) An automobile moving at 80 m/s begins (at t = 0) to accelerates at the rate of 4 m/s 2. What will be its average velocity (in m/s) during the time interval from t = 2s to t = 5s? A) 90 B) 91 C) 92 D) An object's velocity changes from 30 m/s to 80 m/s while accelerating uniformly during a five-second time period. How far (in m) did the object travel during this time? A) 215 B) 275 C) 305 D) 365 Page 5