PHYSICS DEPARTMENT PHY 3053 EXAM #1 FEB. 3, 1995 Print Name:_______________________________ Section No. :________________ Student No.:__________________________ Signature: _______________________________ 1. CODE YOUR TEST NUMBER ON YOUR GREEN ANSWER SHEET (USE 76-80 FOR THE 5-DIGIT NUMBER). CODE YOUR NAME, SECTION NUMBER AND STUDENT NUMBER ON YOUR ANSWER SHEET. DARKEN CIRCLES COMPLETELY (ERRORS CAN OCCUR IF TOO LIGHT). 2. PRINT YOUR NAME, SECTION NUMBER AND STUDENT NUMBER ON THIS SHEET AND SIGN IT ALSO. 3. FOR MOST QUESTIONS, ONE OF THE ANSWERS LISTED WILL BE CONSIDERED CORRECT. SOMETIMES BY ACCIDENT, NONE OF THE LISTED ANSWERS IS CLOSE ENOUGH TO BE CONSIDERED CORRECT. IN THAT CASE THE CORRECT ANSWER WILL BE NO ANSWER. 4. DO ALL SCRATCH WORK ON THIS EXAM TO THE RIGHT OF THE QUESTIONS, AND ANYWHERE ELSE ON THE EXAM. AT THE END OF THE TEST, THIS EXAM PRINTOUT IS TO BE TURNED IN. NO CREDIT WILL BE GIVEN WITHOUT BOTH THE ANSWER SHEET AND PRINTOUT, WITH THE SCRATCH WORK WHICH MOST QUESTIONS DEMAND OF ANYONE. 5. WORK THE QUESTIONS IN ANY ORDER. INCORRECT ANSWERS ARE NOT TAKEN INTO ACCOUNT IN ANY WAY; YOU MAY GUESS AT ANSWERS YOU DON'T KNOW IF YOU FEEL THAT A CORRECT ANSWER IS LISTED. GUESSING ON ALL QUESTIONS WILL MOST LIKELY RESULT IN FAILURE. 6. BLACK THE CIRCLE OF YOUR INTENDED ANSWER COMPLETELY, USING A NUMBER 2 PENCIL ON THE ANSWER SHEET. DO NOT MAKE ANY STRAY MARKS OR THE ANSWER SHEET MAY NOT BE READ PROPERLY. 7. AS AN AID TO THE EXAMINER (AND YOURSELF) IN THE CASE OF POORLY MARKED ANSWER SHEETS, PLEASE CIRCLE YOUR SELECTED ANSWER ON THE EXAMINATION SHEET. 8. GOOD LUCK!!!! ------------------------------------------------------------------------ >>>>> BEFORE YOU FINISH <<<<< FOLD THE COMPUTER PRINTOUT SO YOUR NAME IS ON TOP, INCLUDE ANY FIGURE SHEET INSIDE THE PRINTOUT. HAND IN THE GREEN ANSWER SHEET SEPARATELY. ------------------------------------------------------------------------ Earth's radius: 6.38 x 10**6* m Earth's mass: 5.98 x 10**24* kg Newton's constant: 6.67 x 10**-11* N m**2*/kg**2 QQ Find the magnitude and direction of the sum of two vectors. The first vector has x and y components 3 and 2, respectively; the second vector has x and y components 7 and 2, respectively. In each of the five choices below the magnitude is the first number while the second number is the angle, in degrees, measured counter-clockwise from the positive x axis. AA (1) 10.8, 21.8 (2) 9.2, 68.2 (3) 3.6, 33.7 (4) 7.3, 15.9 (5) 10.0, 4.0 QQ A vector has magnitude 10 and direction 110 degrees measured counter-clockwise from the positive x axis. What are its x (first number) and y (second number) components? AA (1) -3.4, 9.4 (2) 3.4, 9.4 (3) 10.6, -29.2 (4) 9.8, 1.7 (5) -27.5, 10.0 QQ A car is moving with velocity 5 m/s along the positive x axis. At time t = 0 the car is at position x = 0 and its driver begins to break with acceleration -1 m/s**2*. What is the car's position at time t = 2 s? AA (1) 8 m (2) 6 m (3) 3 m (4) 12 m (5) 10 m QQ An apple falls from a tree of height 3 m, near sea level on Earth. What is the magnitude of the apple's velocity at the instant it strikes the ground? AA (1) 7.7 m/s (2) 9.8 m/s (3) 5.4 m/s (4) 0.8 m/s (5) 6.0 m/s QQ A 20 kg object is held by gravity on a horizontal surface whose coefficients of static and kinetic friction are 1/2 and 1/3, respectively. If the object has an initial velocity of +2 m/s along the positive x axis, what is the x component of the force of friction on the object. AA (1) -65 N (2) +65 N (3) -98 N (4) +98 N (5) +7 N QQ A man walks forward on a train which is moving with velocity 27.8 m/s relative to its stationary tracks. If the man's speed relative to the train is .5 m/s, what is his velocity relative to the train tracks? AA (1) 28.3 m/s (2) 27.3 m/s (3) .5 m/s (4) 27.8 m/s (5) -27.3 m/s QQ A projectile is fired from the ground at an angle of 75 degrees above the horizon and with an initial velocity of 1000 m/s. What are its range (x component of position) and altitude (y component of position) at time t = 3 s after the firing? In each of the choices below the first number represents the range and the second number gives the altitude. AA (1) 776 m, 2,854 m (2) 259 m, 937 m (3) 776 m, 2,898 m (4) 2,898 m, 732 m (5) 259 m, 966 m QQ A basketball player makes a foul shot at a horizontal distance of 5 m from a goal which is 3 m high. The ball leaves his hands at a height of 2 m, with an unknown initial velocity directed 55 degrees above the horizon. What is the ball's initial velocity? AA (1) 7.79 m/s (2) 11.0 m/s (3) 8.7 m/s (4) 9.8 m/s (5) 1.1 m/s QQ The theory of quantum chromodynamics describes the forces that colored objects such as quarks and gluons exert on one another. Suppose that a red u quark of mass 5 MeV exerts a force of +5 x 10**9* N along the positive x axis on a blue d quark of mass 10 MeV. What is the x component of the force in Newtons exerted by the blue d quark on the red u quark? AA (1) -5 x 10**9* (2) -10**10* (3) 2.5 x 10**9* (4) 3.3 x 10**-9* (5) insufficient data QQ The total force on an object of mass 17 kg has magnitude 71 N and direction 200 degrees measured counter-clockwise from the positive x axis. What is the y component of the object's acceleration? AA (1) -1.43 m/s**2* (2) 3.92 m/s**2* (3) -66.7 m/s**2* (4) -413 m/s**2* (5) -.700 m/s**2* QQ An astronaut is being held on the surface of one of the outer planets of the solar system, but he does not know which one. To find his location he attempts to infer the acceleration due to gravity on the planet's surface. He does this by observing that the time for his pencil to fall a distance of 1 m is .426 s. The five choices below give the acceleration of gravity on the surfaces of the outer planets. Which one is he on? AA (1) 11.0 m/s**2*, Neptune (2) .03 m/s**2*, Pluto (3) 22.9 m/s**2*, Jupiter (4) 9.05 m/s**2*, Saturn (5) 7.77 m/s**2*, Uranus QQ A block of mass 2 kg rests on a frictionless table. It is connected by a frictionless pulley to a 1 kg block as shown in Figure 1. What is the magnitude of the acceleration of the 2 kg block? AA (1) 3.3 m/s**2* (2) 9.8 m/s**2* (3) 0.0 m/s**2* (4) 4.9 m/s**2* (5) 6.5 m/s**2* QQ What is the space shuttle's period of rotation if has a circular orbit 1.5 x 10**5* m above the Earth's surface? AA (1) 5,250 s (2) 5,130 s (3) 16 s (4) 836 s (5) 34,700 s QQ Suppose three spherical masses lie on the x axis at positions x = -10 m, 0 m, and +5 m as shown in Figure 2. The sphere at x = -10 m has a mass of 8 kg while the spheres at x = 0 m and +5 m both have mass 4 kg. What is the x component of the total gravitational force exerted on the central mass? The five choices are given in units of 10**-11* N. AA (1) +2.14 (2) 0.00 (3) -107. (4) -6.40 (5) +6.40 QQ A car moves at constant around an unbanked circular track of radius 1000 m. What is the maximum speed if the tires' coefficient of static friction is .5? AA (1) 70.0 m/s (2) 99.0 m/s (3) 22.4 m/s (4) 140 m/s (5) 0.00 m/s QQ A 150 kg crate is released from an airplane which is flying at a constant altitude of 9,000 m with a ground speed of 120 m/s. As the crate falls the wind applies a constant horizontal force of 250 N opposite to its horizontal motion. How far does the crate move horizontally before it hits the ground? AA (1) 3,610 m (2) 2,110 m (3) 5,150 m (4) 6,680 m (5) 92,600 m QQ Hooke's law is, F = k x, and it gives the magnitude of the force exerted by a spring which has been stretched a distance x beyond its equilibrium length. The spring constant k is a characteristic of the spring. What are possible units for k? AA (1) N/m (2) N-m**2*/kg**2* (3) s**2*/kg (4) kg-m**2*/s**2* (5) N QQ At the instant a traffic light turns green, a car that has been waiting at rest begins to accelerate at a constant rate of 2.5 m/s**2*. At this same instant a truck, traveling with a constant speed of 15 m/s, passes the car. How far beyond the light does the car overtake the truck? AA (1) 180 m (2) 90 m (3) 12 m (4) 19 m (5) 26 m