MCAT Question of the Day

Correct Answer: C. Inversely proportional to the square of the distance between them.

The Law of Universal Gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

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Correct Answer: B. 250 N.

The center of gravity occurs 4.0 m from the pivot point. At equilibrium:

(2.0 m)(500 N) = (4.0 m)(w)
w = ½ (500N) = 250 N

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Correct Answer: D. 90 cm³/s.

Q = Av = (3.0 cm²)(30 cm/s) = 90 cm³/s.

Fun Fact: That’s the amount of a soda can every 4 seconds!

Work is force times distance moved. A body held at a given height is not in motion, so work is no longer being performed on it.

The period, T, is equal to:
T = 2(pi) sqrt(L/g)

Thus, the period is directly proportional to the square root of the length. Any increase in L will produce an increase in T. The mass of the box does not influence the period.

60 W represents the power usage of the bulb. Power is the product of current and voltage. Thus:

The force is inversely proportional to the square of the distance between the point charges. Since the distance is doubled, the force must be quartered.

v = v(0) + at. Here is a quick tip to speed up a question like this on the exam. Estimate the acceleration due to gravity using a = -g = -9.8 m/s^2 ~ -10 m/s^2. The velocity is approximately:

The closest answer to 20 m/s is A.

Conservation of energy means the sum of the kinetic and potential energies must be the same at the start of the jump and at its maximum height:

(Initial energies on the left and final energies on the right.)

There is no height initially, so there is no initial potential energy. At the top of the jump there is no velocity, so there is no final kinetic energy. This gives:

Therefore:

The mass of the vaulter cancels out.

The speed is constant but the direction of the car is constantly changing, thus the velocity is constantly changing, which in turn means the car undergoes acceleration. Since only the direction is changing, only the radial acceleration component is nonzero. The tangential acceleration component is zero.