PHYSICS DEPARTMENT
PHY2004, Stanton               Exam #2                 October 24, 1996
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                        g = 32.2ft/s**2  = 9.8 m/s**2
                           1 hp = 746 watts
    * * Problems marked with a * (* *) are more (most) difficult. * *
  1. An 80 kg skier, skies down a slope of 30 degrees (see figure 1). How much work is done (in Joules) BY GRAVITY when the skier is at a height 100 m below the originial height?

    1. 7.84 x 104
    2. -7.84 x 104
    3. 3.92 x 104
    4. -3.92 x 104
    5. 8.0 x 103


  2. A fireman jumps down a 20 foot fire pole. Neglecting all friction (both with the pole and with the air) what is the speed, in miles per hour, of the fireman as he reaches the bottom of the slide?

    1. 24.5
    2. 35.9
    3. 19.8
    4. 13.5
    5. 17.3


  3. In figure 2 is shown a wire along which a 50-g bead slides. If friction forces can be ignored, and the bead starts from rest at A, how fast will it be going at point B in m/s?

    1. 4.4
    2. 3.1
    3. 7.0
    4. 4.9
    5. 3.5


  4. A crane is operated by a 100 hp motor. If it lifts its load at the rate of 0.1 m/s, then what is the maximum mass (in kg) that the crane can lift? Assume the crane is 100% efficient.

    1. 7.6 x 104
    2. 7.5 x 105
    3. 102
    4. 1.0 x 105
    5. 746


  5. A simple machine requires an input force of 80 N acting over a distance of 40 m to raise a 3500 N weight by 30 cm. What is the % efficiency of this machine?

    1. 33
    2. 44
    3. 100
    4. 55
    5. 25


  6. A pulley system consists of two sets of two pulleys as shown in figure 3. If the system has an efficiency of 85%, Then how much weight W, in lbs., can be lifted with a 150 lb input force?

    1. 510
    2. 600
    3. 638
    4. 255
    5. 383


  7. What is the IMA of the lever system shown in figure 4?

    1. 0.5
    2. 2
    3. 3
    4. 0.33
    5. 1.5


  8. A certain hydraulic press has an output piston of 10.0 cm in diameter. The input piston has a diameter of 0.5 cm. How large a force (in N) must be supplied to the input piston to provide an output force of 30,000 N? Assume the press is ideal.

    1. 75
    2. 1500
    3. 150
    4. 750
    5. 600


  9. How large an impulse (in N-s) does a 20 g bullet moving at 400 m/s exert on a tree as it strikes and comes to rest in the tree?

    1. 8
    2. 8000
    3. 20
    4. 20,000
    5. 1600


  10. * A 2.5 kg ball is moving at 5.0 m/s in the +y direction. It strikes a stationary 6.0 kg ball and bounces off so that it is going 0.75 m/s in the +x direction. What is the x-component of the 6.0 kg ball after the collision (in m/s)?

    1. -0.31
    2. 0.31
    3. 2.1
    4. -2.1
    5. 3.2


  11. An 80 kg man on ice skates is moving at 6.5 m/s when he runs squarely into the back of a 60 kg women on ice skates standing at rest. He holds onto her and they move off together. What is their speed (in m/s) after the collision?

    1. 3.7
    2. 2.8
    3. 4.9
    4. 8.7
    5. 3.3


  12. * * Particle A has mass 1 kg and is initially moving with a velocity of 2 m/s toward particle B which has mass 2 kg and is initially at rest. If they collide head on (i.e. in one dimension) and the collision is perfectly elastic, then what is the velocity (in m/s) of particle B after the collision?

    1. 1.3
    2. 1.0
    3. -0.7
    4. 2.7
    5. 0.7


  13. * What is the angular speed, in RADIANS/s of the Earth going around the Sun?

    1. 2.0 x 10-7
    2. 3.2 x 10-8
    3. 7.2 x 10-4
    4. 7.3 x 10-5
    5. 4.8 x 10-6


  14. After the power is turned off to a motor whose shaft speed is 5000 revs/min, the motor takes 10.0 s to stop. Through how many REVOLUTIONS did the shaft turn while the motor came to a rest? Assume uniform acceleration.

    1. 417
    2. 833
    3. 208
    4. 25,000
    5. 500


  15. What is the maximum angular velocity (in RAD/s) that a 2 kg mass on a 1.5 m rope can be swung if the rope can support a tension of 350 N before breaking?

    1. 10.8
    2. 5.4
    3. 67.9
    4. 16.2
    5. 117


  16. If a bicycle is travelling at 40 km/h, how fast are its 70 cm diameter wheels turning in REVS/MIN?

    1. 303
    2. 5.1
    3. 152
    4. 48
    5. 952


  17. A pendulum (shown in figure 5) has a WEIGHT of 98 N and length of 10 m. What is the moment of inertia of the pendulum about its fixed point in (kg-m2)? (Assume the rope has no mass.)

    1. 1000
    2. 9800
    3. 980
    4. 100
    5. 4900


  18. What is the moment of inertia for rotation in-plane about the center sphere for the masses shown in figure 6 in units of (kg-m2)? Take m = 2.0 kg and r = 1.0 m. The black spheres have mass 2m and the white spheres have mass m.

    1. 24
    2. 12
    3. 20
    4. 10
    5. 16


  19. What is the rotational kinetic energy (in Joules) for a wheel that is rotating at 5.0 REVS/s if I for the wheel is 2.7 kg-m2?

    1. 1332
    2. 34
    3. 2665
    4. 68
    5. 46


  20. A figure skater is spinning at the rate of 3 REVS/sec. He pulls in his arms so that his new radius of gyration is 1/2 his original radius of gyration. What is his new angular velocity in REVS/sec?

    1. 12
    2. 6
    3. 0.5
    4. 0.75
    5. 1.5