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Need Help With College Physics

  1. Jul 26, 2005 #1
    Need Help With College Physics!!!!!!!!!!

    alright i have some homework questions i need help with, any help would be greatly appreciated:

    1.A 300 g baseball traveling at 30 m/s is struck by a bat in the direction from which it came at 40 m/s. Find the impulse of the force on the baseball.

    2.A solid cylinder of mass 8 kg and diameter 20 cm is rotated about an axis parallel to its central axis at a distance of 10 cm from the cylinder. The rotational inertia of the cylinder about the parallel axis is:

    3.If a solid cylinder, a hoop and a solid sphere of the same mass are rolled down simultaneously from the same height on an inclined plane, in which order will the objects reach the bottom of the incline?

    4.A 3 kg bowling ball traveling with a velocity of 3 m/s collides head-on with another bowling ball of the same mass traveling with a velocity of - 2 m/s. If the collision is perfectly elastic, the velocities of the bowling balls after the collision is:

    5.The center of mass of three objects is located at (1, 0). One object with a mass of 5.0 kg is at (- 2, - 1) and a second object with a mass of 2.0 kg is at (0, 0). Find the coordinates of the third mass of 3.0 kg.

    6.Water is pumped through a pipe to a tank at the top of a building. The pressure of the water at ground level is 2.2 x 105 Pa and at the tank, the pressure is atmospheric. If the diameter of the pipe is the same throughout, find the height at which the tank is located. Atmospheric pressure may be assumed as 1.0 x 105 Pa and g as 9.8 m/s2.

    7.A force of 1.0 x 103 N is applied to a steel rod of length 1 m and a circular cross-section of area 10 cm2. Find the elongation of the rod. Young's modulus for steel is 2.0 x 1011 Pa.

    8.A 200 g ball hits a wall perpendicularly with a velocity of 30 m/s and rebounds back perpendicularly with a velocity of 20 m/s. If the collision lasts for 5 milliseconds, find the average force exerted by the ball on the wall.

    9.A disk with a mass of 50 kg and radius 0.40 m is rotated about its axis by a motor. The disk starts from rest and rotates at 120 rev/min in 10 s. Find the torque, assuming it to be a constant.

    10.The magnitude of the momentum of a particle is 32 kg m/s at a certain instant. If the velocity has a magnitude of 20 m/s at that instant, the mass of the particle is:

    11.A star rotates about its axis through a diameter once in 50 days. At the end of its life, the star collapses to one-hundredth of its original diameter. The rate of rotation of the collapsed star will be:

    12.The crankshaft of an engine is accelerated from rest at the uniform rate of 4.0 rad/s2 for 30 s. Find the rotational speed of the crankshaft at the end of 30 s in rev/min.

    13.The gauge pressure at a depth of 17 m in water is equal to:

    14.A uniform solid sphere of mass 5 kg and radius 30 cm is rotating about an axis through its center at the rate of 180 rev/min. Find the kinetic energy of the sphere. The rotational inertia of a uniform sphere is 2/5 MR2.

    15.A log of wood is floating in water with 40% of its volume above the surface of the water. If the volume of the log is 0.4 m3, find the mass of the log.

    alright thats it, PLEASE HELP ME with any of these THANKS!!!!!!!!!
  2. jcsd
  3. Jul 26, 2005 #2
    please tell us what you have done with these problems yourself.

    us showing you how to solve 15 problems from start to finish is a tall order! and it also will be beneficial to you to make an attempt. that way you'll learn and remember what difficulties you had and how to resolve these difficulties.
  4. Jul 26, 2005 #3
    First of all you need to show some effort before people will explain things, however I will tell you what you should look at the find the answer:

    1. This problem looks like it involves the impulse-momentum theorem
    2. Condiser the parallel axis theorem
    3. Use an extended FBD on the objects and remember a = alpha*radius
    4. This problem simply requires conservation of momentum
    5. Look at the equation for the center of mass for a particle
    6. There is an equation that relates pressure, density, g, and h
    7. Stress = Young's Modulous * Strain however you need to extended the
    definitions of stress and strain
    8. Impulse momentum theorem once again
    9. The sum of torques is the product of the moment of inertia and the
    angular acceleration.
    10. This is the easiest problem yet, just look up the equation for linear
    11. Consider the conservation of angular momentum
    12. This just requires some basic rotational kinematics
    13. You will use the same equation as you did in problem 6
    14. KErotational = 1/2*I*omega^2
    15. This is the toughest problem yet, you will need to use the same equation
    as you did in problem 6 again as well as the fact that Force is the
    product of pressure and area. Remember, the volume of an object is its
    cross-sectional area multiplied by its height.

    Good Luck!
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