Physics I Exam 1 Fall 2015 (version A)

Transcription

1 Physics I Exam 1 Fall 2015 (version A) Recitation Section Number Last/First Name (PRINT) / Last 3 Digits of Student ID Number: Fill out the above section of this page and print your last name on the top of each of the following pages. Answer all questions, beginning each new question in the space provided. Show all work. Show all formulas used for each problem prior to substitution of numbers. Label diagrams and include appropriate units for your answers. You may use an alphanumeric calculator (one which exhibits physical formulas) during the exam as long as you do not program any formulas into memory. By using an alphanumeric calculator you agree to allow us to check its memory during the exam. Simple scientific calculators are always appropriate! A Formula Sheet is attached to the back of this examination. (For your convenience you may carefully remove it from the exam. Please take it with you at the end of the exam or throw it in a waste basket.) Be Prepared to Show your Student ID Card Score on each problem: I. (25) II. (25) III. (25) IV. (25) Total Score (max. = 100 pts)

2 2 Part I. (25 points) Put a circle around the letter that you think is the best answer. I-1 The figure shows the position of an object (moving along a straight line) as a function of time. Assume two significant figures in each number. Which of the following statements about this object is true over the interval shown? A) The object is accelerating to the left. B) The object is accelerating to the right. C) The acceleration of the object is in the same direction as its velocity. D) The average speed of the object is 1.0 m/s. I-2 The graph shows the position versus time for an object during the time interval of t = 0.0 s to t = 9.0 s. (Assume that all numbers are accurate to two significant figures.) Which of the following results are correct according to the figure? A) average speed = 0.11 m/s; average velocity = 0.44 m/s B) average speed = 0.77 m/s; average velocity = 0.11 m/s C) average speed = 0.17 m/s; average velocity = 0.89 m/s D) average speed = 0.56 m/s; average velocity = 0.11 m/s E) average speed = 0.89 m/s; average velocity = 0.56 m/s

3 3 I-3 The displacement of a particle is given by yt = t t + t m. Which of the following is correct? 3 2 ( ) A) acceleration = 2.4t + 11 m/s 2 B) velocity = 2 1.2t + 14t 3 m/s C) acceleration = 14 m/s 2 D) acceleration = 2.4t 14 m/s 2 E) velocity = 2 t + 14t 3 m/s I-4 For an object that travels at a fixed speed along a circular path, the acceleration of the object is A) larger in magnitude the smaller the radius of the circle. B) in the same direction as the velocity of the object. C) smaller in magnitude the smaller the radius of the circle. D) in the opposite direction of the velocity of the object. E) zero. I-5 Two children are riding on a merry-go-round. Child A is at a greater distance from the axis of rotation than child B. Which child has the larger angular speed? A) Child A B) Child B C) They have the same zero angular speed. D) They have the same non-zero angular speed. E) There is not enough information given to answer the question.

4 4 Part II (25 points) The total stopping distance (for maximum braking acceleration) of a car traveling at a speed of 30 m/s is 70 m which includes the distance traveled during the driver s reaction time of 0.55 s. A) Determine the distance the car travels during the driver s reaction time. B) Determine the maximum braking acceleration. C) Suppose that the same car was traveling at 40 m/s, determine the new total stopping distance under maximum braking acceleration. D) For the motion described in part C) determine the time elapsed while under braking acceleration. E) For the motion described in part C) draw and label a position-versus-time graph. Label the graph with as much information as possible. Describe each type of curve that is in the graph.

5 Part III (25 points) Consider the following two vectors: A= 4iˆ 2ˆj B= 3iˆ+ 5ˆj 5 R= A 4B A) Determine the magnitude and direction of the two vectors, A and B. B) Determine the components for the resultant vector R= A 4B. C) Determine the magnitude and direction of the vector R. D) Draw a coordinate system and put the three vectors on it (begin each vector at the origin).

6 Part IV (25 points) 6 A projectile is shot upward from from a depth of 100 m (i.e. below the ground). A) Determine the maximum height of the projectile (above the ground) if the initial vertical component of its velocity is 80 m/s. B) Determine the initial angle that the projectile is shot at if the initial speed is 90 m/s. C) Determine the time that the projectile is in the air given that it travels 620 m horizontally before it hits the ground. Hint: First find the initial horizontal component of the velocity. D) Determine the direction of the projectile as it hits the ground.