95.141 Physics I Exam 1 Spring 015 (version A) Section Number Section instructor Last/First Name (PRINT) / Last 3 Digits of Student ID Number: 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. Write your name and section number at the top of each page in the space provided and write the name of your section instructor in the place provided in the cover sheet.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. (5) II. (5) III. (5) IV. (5) Total Score (out of 100 pts)
Last Name only (PRINT) Part I. (5 points each) Put a circle around the letter that you think is the best answer. I-1 The position x, in meters, of an object is given by the equation x = A + Bt + Ct, where t represents time in seconds. What are the SI units of A, B, and C? A) m, m, m B) m, s, s C) m, s, s D) m, m/s, m/s E) m/s, m/s, m/s3 I- When can we be certain that the average velocity of an object is always equal to its instantaneous velocity? A) always B) never C) only when the velocity is constant D) only when the acceleration is constant E) only when the acceleration is changing at a constant rate I-3 Suppose that an object is moving with constant nonzero acceleration. Which of the following is an accurate statement concerning its motion? A) In equal times its speed changes by equal amounts. B) In equal times its velocity changes by equal amounts. C) In equal times it moves equal distances. D) A graph of its position as a function of time has a constant slope. E) A graph of its velocity as a function of time is a horizontal line.
3 Last Name only (PRINT) I-4 The motions of a car and a truck along a straight road are represented by the velocitytime graphs in the figure. The two vehicles are initially alongside each other at time t = 0. At time T, what is true about these two vehicles since time t = 0? A) It is not possible to tell whether the car or truck traveled more distance. B) The truck will have traveled further than the car. C) The car will have traveled further than the truck. D) The truck and the car will have traveled the same distance. E) The car will be traveling faster than the truck. I-5 As part of an exercise program, a person walks south at a speed of.00 m/s for 60.0 minutes. The person then turns around and walks north a distance 3000 m in 5.0 minutes. What is the person's average velocity during the entire motion? A) 0.84 m/s south B) 1.93 m/s south C).00 m/s south D) 1.79 m/s south E) 800 m/s south
4 Part II (5 points each part total of 5 points) Last Name only (PRINT) A car passes a location labeled as x = 0 at t = 0. It is traveling at 15 m/s in the positive x- direction. For the first 4.0 seconds it keeps the same velocity; for the next 3.0 seconds it has an acceleration of -3.5 m/s ; and the for the next.0 seconds has an acceleration of +4.5 m/s. A) Draw and label a motion diagram for the car. B) Determine the location of the car at 7.0 seconds after it passes x = 0. C) Determine the velocity of the car at 7.0 seconds after it passes x = 0. D) Determine the location of the car at 9.0 seconds after it passes x = 0. E) Determine the velocity of the car at 9.0 seconds after it passes x = 0.
5 Last Name only (PRINT) Part III (5 points each part total of 5 points) A particle s motion (displacement, velocity, acceleration) is described by the following equations: 3 t t xt ( ) = 7 + 10t 3 vt ( ) = t 7t+ 10 at () = t 7 Assume that standard S.I. units are used. A) Determine the displacement during the time interval from 0 to seconds. B) Determine the average velocity during the time interval from 1 to seconds. C) Determine the instantaneous velocity at 0.75 seconds. D) Determine the time (it any) that the acceleration is zero. E) Determine the average acceleration during the time interval from 0 to seconds.
6 Last Name only (PRINT) Part IV (5 points each part total of 5 points) Vector A has a magnitude of 75.0 cm and points at 30 degrees above the positive x-axis. Vector B has a magnitude of 5.0 cm and points along the negative x-axis. Vector C has a magnitude of 40.0 cm and points at 45 degress below the negative x-axis. A) Draw the three vectors appoximately to scale on a standard xy-coordinate system with all of their tails at the origin. (Put this on the left side of the page.) B) To the right of the above, graphically contruct the resultant vector R = A B + C. C) Write down each of the three vectors separately using unit vectors. D) Determine the components of the resultant vector R. E) Determine the magnitude and direction of the resultant vector R.
7 Formulae for 95.141 Exam #1 Spring 015 Graphical Analysis r vavg = t t = t t a v a avg inst inst f v = t dr = dt i dv = = dt r = r r (slope of position versus time) f i (slope of velocity versus time) (slope of position versus time at a specific time) d r dt (slope of velocity versus time at a specific time) S f = S i + area under velocity versus time for Δt = t f - t i V fs = V is + area under acceleration versus time for Δt = t f - t i Analytical Analysis (for constant linear acceleration) S 1 f = Si + vis + t as t vfs = vis + as t v = v + a S fs is S ( )