The only two factors that affect a pendulum's frequency are the acceleration due to gravity (g) and the length of the pendulum's string (L). This can be seen in the following formula: . 

Both the length of the pendulum's string and the angle of displacement affect the maximum velocity of the pendulum. Increasing the length of the pendulum's string and increasing the angle of displacement both increase the distance the pendulum must travel in a single period, increasing its potential energy at its maximum height, and therefore the maximum velocity at its lowest point.

The key to answering this question is to recall the following important formula for a simple pendulum: .

For a pendulum, the angular velocity is given by the equation , where  is the acceleration due to gravity and  is the length of the pendulum. Of the available answer choices, only changing the length of the string will effect the angular velocity. does not depend on mass or the release point of the pendulum.

The frequency of a pendulum is given by the relation  .

Since gravity on the moon is one sixth of the gravity on Earth, frequency on the moon will be  that on earth.

If the frequency on Earth is , then the frequency of this pendulum on the moon is .

The period of a pendulum is given by the formula:

 is the length of the pendulum arm or string, and  is the acceleration due to gravity. Gravity is constant, suggesting that the only way to manipulate the period of the pendulum is by adjusting the length of the string. Doubling the length of the pendulum arm would therefore increase the period. Since mass does not appear in the equation, it has no effect on the period of a pendulum.

Mechanical energy is the sum of potential energy and kinetic energy. Mechanical energy is conserved, unless there is intervention by a non-conservative force (such as friction).

The total energy in the system is determined by how far the pendulum is raised before release, based on the initial potential energy.

The potential energy is all converted to kinetic energy as the pendulum swings through the bottom, or mid-point of its excursion.

Once the pendulum is set in motion, the mechanical energy is constant in a frictionless system.

Hooke’s law, which is applicable to simple harmonic motion, states the relationship between force (F) and displacement (d).

k is equal to the spring constant. The ratio of F (force) to x (displacement) will be equal to the magnitude of k. In our set-up, the force is equal to the weight of the pendulum, so the ratio of weight to displacement is equal to the spring constant. This is true of all pendulums, and is given by the equation .

This problem covers conservation of energy in the form of a pendulum:

If the initial state is when the pendulum is at its highest point, and the final state is when the pendulum is at its lowest state, we can rewrite:

Substituting in our expressions:

Rearranging for final velocity:

We can calculate the height using the maximum angle the pendulum makes to the vertical. At this point, the pendulum covers a vertical distance of:

Therefore, the height above the lowest point is:

Now, we just need to find out what the net downward acceleration is. Normally gravity is 10, but the elevator is accelerating upward at a rate of . Therefore the percieved gravitational acceleration is .

Plugging in all of our values:

This problem focuses on understanding simple harmonic motion. The formula to identify the frequency, or cycles per second, that the mass moves is given below, where  is the spring constant of the spring and  is the mass of the object attached.

Notice that the frequency does not depend on how far the mass is displaced originally. If the mass is displaced more, it will simply be moving faster when it goes through the equilibrium position. It will not, however, move through the equilibrium position any more frequently than it would if it had been displaced less. 

Increasing the mass of the object attached would increase the denominator in the formula, and would therefore decrease the frequency of the harmonic motion.

Increasing the spring constant, , would increase the numerator of the formula, which would result in an increase in the frequency on the motion. The spring constant is directly proportional to the stiffness of the spring; thus, increasing stiffness will increase frequency.