First Examination
Physics 103
23 September 1980

#1.  To change 60 km/hr to ft/sec, the appropriate conversion is
Answer:

a) (60 km/hr)   ´ (1 hr/60 min) ´ (1 min/60 sec)  ´ (1000 m/1 km) ´  (3.28 ft/1 m)
b) (60 km/ hr)   ´ (1 hr/60 min) ´ (1 min/3600 sec)  ´ (1 km/1000 m) ´  (3.28 ft/1 m)
c) (60 km/ hr)   ´ (1 hr/60 sec) ´ (1000 m/1 km) ´  (3.28 ft/1 m)
d) (60 km/ hr)   ´ (1 min/60 sec) ´ (1 hr/60 min)  ´ (1000 m/1 km) ´  (3.28 ft/1 m)
e) (60 km/ hr)   ´ (60 min/1 hr) ´ (1 min/60 sec)  ´ (1 m/1000 km) ´  (3.28 ft/1 m)

#2.  A vector R, as shown in the sketch, has a magnitude of 10 m and makes an angle of 30o with the +x-axis.  The vector R is most closely equal to


Answer:
a)i 10 m     b) -i 5 m + j 5 m     c) -i 5 m + j 8.6 m    d) i 5 m + j 15 m     e) i 8.6 m + j 5 m

#3.  We are given the vectors

A = 3 i + 4 j
B = i - 2  j + 2 k
Let q be the angle between A and B. Which of these statements is true?
Answer:
a) cos q = -1/3      b)  tan q = 3/4      c)  tan q = 2      d)  cos q = 11/15      e)  sin q = 2/5     

#4.   A car travels 6 km EAST for 4 minutes, then 8 km NORTH for 6 minutes. The average velocity (in km/hr) is most nearly equal to

Answer:

a) 84 km/hr Northeast
b)1.4 km/hr Northeast
c) 1 km/hr at 53.1o North of East
d) 60 km/hr at 53.1o North of East
e) 60 km/hr Northeast

#5.  The displacement vs time curve for an object is given below.  The corresponding velocity vs time curve would look like: 


Answer:

a)
b)
c)
d)
e)

#6.  A rocket blasts off vertically from rest.  A graph of its vertical velocity (m/sec) versus time (sec) is shown.  The average acceleration of the rocket during the first 5 seconds of flight is most nearly equal to


Answer:
a) 0   b) 100 m/sec2    c) 500 m/sec2     d) 1500 m/sec2      e) 250 m/sec2

#7. A truck starts from rest and moves with constant acceleration.  At time t1 it has a speed of 10 m/sec, and at a later time t2 it has a speed of 15 m/sec.  During the time interval (t1, t2) it has moved 100 mNote:  This is one-dimensional motion. The time interval between tand t2 is
Answer:
a) 8 sec   b) 10 sec   c) 20 sec    d) 6 and 2/3 sec      e) 4 sec

#8. In Problem #7, the acceleration of the truck is
Answer:
a) 0.25 m/sec2     b) 0.625 m/sec2     c) 1.5625 m/sec2     d) 0.5 m/sec2    e) indeterminate 

#9. An "el" train accelerates uniformly from rest to 60 mi/hr in 15 seconds.  It maintains that constant velocity for 45 seconds, and then decelerates to rest in 10 seconds. The total distance traveled is most nearly equal to
Answer:
a) 3450 ft     b) 4200 ft      c) 6160 ft    d) 4180 ft    e) 5060 ft

#10. An object is dropped from rest from a bridge 36 feet above a lake.  It falls with a uniform acceleration of 32 ft/sec2 until it hits the water; then it sinks with its constant "splashdown" velocityThree seconds after it was dropped, the object reaches the bottom of the lake.  What is the depth of the lake?  
Answer:
a) 144 ft    b) 72 ft  c) 108 ft   d) 36 ft   e) 40 ft

#11. A ball is thrown vertically straight up (in the +y direction).  At the position of its maximum altitude it is true that
Answer:
a) both acceleration and velocity are zero
b) its acceleration is zero, but not its velocity
c) its acceleration is -g and its velocity is negative
d) its acceleration is -g and its velocity is positive
e) its acceleration is -g and its velocity is zero

#12. A football player kicks a ball 200 feet (ground to ground) from its initial position. If the angle of the initial velocity with respect to the ground is 300, the magnitude of the initial velocity is most nearly equal to
Answer
a) 86 ft/sec     b) 48 ft/sec        c) 80 ft/sec       d)7390 ft/sec        e) 2263 ft/sec

#13. A bullet is fired with an initial velocity v0 at a target x feet away.   the expression giving the vertical displacement y from the initial line of sight (x-axis) is:  Hint:  do not neglect gravity.       
Answer

a) y = y0t + ˝gt2    b)  y = x + v0t     c)   y = -gx2/(2v02)      d) y = -v0 t    e) y = gx2/v02 


14. An airplane traveling at 150 m/sec at an angle of 30o below the horizontal, drops a package from a height of 1000 m.  The horizontal displacement of the package when it hits the ground, relative to the drop point, is approximately 
Answer:
a) 1100 m      b) 760 m    c) 3100 m       d) 2100 m       e) 0 m

#15. A car travels around a circular track at a fixed speed of  50 ft/sec in a time of 20 seconds.  The radial acceleration experienced by the car is
Answer:
a) 2.5 ft/sec2, outward   b)5p ft/sec2, inward    c) zero   d) 125 ft/sec2, outward    e) 125 ft/sec2, inward