<p>Please explain how you get the answers to these.</p>
<li><p>A pendulum consists of a bob of mass A hanging from a string of non-zero mass m. Its maximum displacement is pi/4. What is true of the tension in the string?
(A) It is greatest at the top
(B) It is greatest at the bottom
(C) It is uniform throughout
(D) It does not vary when the pendulum is put in motion
(E) It is greatest when the pendulum is in its maximum amplitude</p></li>
<li><p>In general, if the center of mass of a system is raised to a higher gravitational potential and the system is otherwise unchanged,
(A) the system becomes more stable
(B) the system becomes less stable
(C) the total energy of the system decreases
(D) the kinetic energy in the system decreases
(E) the system does work on its environment</p></li>
<li><p>A box of mass m is sliding down a frictionless ramp of length L with an incline of theta to the horizontal. The mass takes t seconds to slide down the ramp. The power exerted by gravity during the slide is
(A) (mgsin(theta))/t
(B) mgtcos(theta)
(C) mgtsin(theta)
(D) (mgLsin(theta))/t
(E) (mgLcos(theta))/t</p></li>
<li><p>A cat of mass mc is sliding across a frictionless surface in a positive x direction with a velocity of magnitude v0 when it collides with a dog of mass md at rest. The dog now travels at an angle 30 degs with respect to the cat’s initial path at a velocity of magnitude v1. The cat travels at an angle of negative 47 degs with respect to the dog’s path of motion with a velocity of magnitude v2. Which of the following is true?
(A) mdv1sin30 = mcv2sin17
(B) mdv1sin30 = mcv2sin47
(C) mdv1cos30 = mcv2cos17
(D) mdv1cos30 = mcv2cos47
(E) mdv1sin30 + mcv2sin17 = mcv0</p></li>
<li><p>An object with a mass of 5 kg is attached to a 1 meter long rope and whirled in a vertical circle. Of the following, which is the greatest speed of the object for which the rope would become slack at the top of its circular path?
(A) 20 m/s
(B) 15 m/s
(C) 10 m/s
(D) 5 m/s
(D) 2 m/s</p></li>
</ol>