Version A write it down immediately on your scantron form                Quiz 2 March 13, 1998

Print Name __________________________ Sign Name ____________________

Fill in the top of each sheet.

The exam is closed book and closed notes. Section (shade one)

In Part I, there are 10 multiple choice Questions.

The answers for the multiple choice Questions are to be placed on the SCANTRON form.

Use a Number 2 pencil to fill in answers on the SCANTRON form

Make sure you give only one (1) answer to each question.

If two or more answers are filled in on the SCANTRON form, the problem will be marked wrong. If you erase an answer on the SCANTRON form, make sure all traces are removed.

For Problems II and III show ALL your work. We want to give you partial credit, but this

can be done only if your work is shown.

Correct answers with unsubstantiated work on Problems II and III will receive ZERO CREDIT. Where you are required to draw motion diagrams, FBDs, etc., you MUST use a straight edge to draw straight lines.

IF YOUR STRAIGHT LINES ARE DRAWN FREEHAND, YOU WILL GET ZERO CREDIT!!!

Here are some useful equations:

S F = ma A = (Ax , Ay) B = (Bx ,By) A + B = (Ax+ Bx , Ay+ By) A - B = (Ax- Bx , Ay- By)

w = mg g = 9.8 m/s2 You can take g = 10 m/s2

v = v0 + at x - x0 = v0 t + ½ at2

2a(x - x0 ) = v2 - v02 x - x0 = ½ (v + v0)t

position = (x , y) = (x0 + v0xt + , y0 + v0yt + ) velocity = (vx , vy ) = (vox+ axt , voy+ ayt )

d = 

ar = v2/r ar = r(2p /T)2 ar = r(2p f)2

Fk = m k N Fsmax = m s N
 
 

I 20 points. Put the answers to these 10 questions on your SCANTRON sheet.

In addition, circle your answers on this examination sheet.

Choose the answer that is closest to the given answer.


  • 1. The 70 N tension force is applied at an angle of 300 to a 20-kg box (see figure). The system remains at rest. The magnitude of the normal force is:

    •  

     

     A) 70 N     B) 130N       C) 140 N         D) 165 N           E) 200 N
     
     
     


    2.   The system shown moves with constant velocity. The coefficient of kinetic friction m k between the block and the incline is  A) 0.20 B) 0.30 C) 0.40 D) 0.50 E) 0.60
     
     
     
     


    3.   A 7-kg block is held against the wall with the force F. The coefficient of static friction m s between the block and the wall is0.6. The minimum force F used to keep the block from sliding is
     
     

    A) 115 N B) 70 N C) 62 N D) 42 N E) 28 N
     
     
     
     
     


    The following two problems refer to the figure shown. An initial position of a moving point is P( 4 , -3). Point moves with constant velocity v(-2m/s , 0.5m/s).

    4.   The position of the point after 4 seconds is

    A) (-4,-1)     B) (0,-2)     C) (-2,-6)     D) (2,-2.5)     E) (6,-3.5)
         
    5.   The distance made during the four seconds is
    A) m     B) m      C) 5 m     D) m     E) m


    6.   A man drives a car over the top of a hill. The crossection of the hill can be approximated by a circle of radius 120 m as in figure. The maximum speed at which he can drive without the car leaving the road at the top of the hill is
    A) 35 m/s    B) 45 m/s     C) 53 m/s     D) 61 m/s     E) 76 m/s
     
     


    7. A space shuttle is orbiting the Earth at an altitude h and at constant speed 8 km/s (see figure). The Earth radius is 6370 km. The altitude h (see figure) of the space shuttle above the Earth is (use g = 10 m/s2):

    A) 10 km B) 20 km C) 30 km D) 40 km E) 50 km
     
     
     

    8. Jill is riding a bicycle along a straight road at constant speed v1=4.2m/s. Her friend, Anita, is driving a car along the same road, in the same direction, at constant speed v2=20m/s. Initially (at time t=0), Anita is 150 m behind Jill. The time Anita catches up to Jill is
    A) 35.9 s      B) 21.4 s       C) 9.5 s       D) 7.5 s         E) 6.2 s

    9. A car travels up a mountain road at the constant speed of 20 km/h, and returns down the same road at speed 60 km/h. The trip ends when the car reaches the point at which it started. The average speed of a car is:
    A) 25 km/h      B) 30 km/h      C) 35 km/h        D) 40 km/h         E) 45 km/h
     
     

    10. One end of a 1.0-m string is fixed, the other end is attached to a 2.0-kg stone. The stone swings in a vertical circle, passing the bottom point at 4.0 m/s. The string tension at this point is about:
    A) 12 N      B) 20 N      C) 32 N       D) 42 N         E) 52 N
     

    II
    Correct answers with unsubstantiated work on Problem II will receive ZERO CREDIT.

    A 1.5-kg ball is connected by two thin strings to a vertical rotating rod. The strings tied to the rod are taut and form two sides of an equilateral triangle (see figure). The tension in the upper string is 40 N.
     

    1. Draw the free Body Diagram for the ball.

    1. Calculate the tension in the lower string. Ans. ______________
    2. Calculate the speed of the ball. Ans. ______________
    3. Calculate the frequency of rotation. Ans. ______________

     
     
     
     

    III
    Correct answers with unsubstantiated work on Problem III will receive ZERO CREDIT.

    The 3.5-kg block A accelerates up the incline from rest. The coefficient of kinetic friction between the block and the incline m k= 0.3. The tension in the rope is 40 N.

    A) In the indicated spaces draw a free-body diagram for block A.

    1. Find the Normal force. Answer: ____________
    2. Find the friction force. Answer ____________
    3. Find acceleration of the block. Answer ____________
    4. Calculate the time for the block to travel the first 3 m up the incline. Answer: ____________
     Free body diagram for A


     
     

    answers:
     
    1 
    165
    2
    0.5
    3 
    115 N
    4
    (-4,-1)
    5
    m
    6 
    35 m/s
    7 
    30 km
    8
    9.5 s
    9
    30km/h
    10 
    52 N

    II 2) 10 N 3) 5.1 m/s 4) 0.52 Hz

    III B) N=26.8 C) 8 N D) a=2.7 E) t=1.5 sec