MCAT Question of the Day

Correct Answer: A. 0.125 cycles/second

Since it takes 4 seconds for the object to travel from one end of its displacement to the other (half a cycle), the time for a full cycle is 2(4 sec) = 8 sec. Thus frequency = 1/T = 1/8 = 0.125 Hz.

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Correct Answer: C. 10 kW.

We can use the equation Power = Force*velocity to solve this problem. The object moves 150 meters in 30 seconds, so the velocity must be (150m/30s) = 5 m/s. Plugging this back into the original equation of P = Fv, then P = (2000 N)(5 m/s) = 10 kW.

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Correct Answer: D. 125 m

The initial horizontal speed is irrelevant. Use this equation: x = (1/2)g(t)² = (1/2)(10)(5)² = 125 m.

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Correct Answer: B. 10 m.

All of the kinetic energy will be transferred into potential energy at the maximum height of the cannonball. The trick is to not replace KE with (1/2)mv², the kinetic energy is already given! Therefore:

KE -> PE -> KE = PE -> KE = mgh -> h = KE/mg = 500 J / (5 kg)(10 N/kg) = 10 m.

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Correct Answer: D. halved.

The centripetal force of the car is mv²/r, where m is the car’s mass, v is the velocity, and r is the radius of the circular track. If we double the radius while keeping everything else uniform, the centripetal force will be halved because they are inversely proportional.

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Correct Answer: A. 20 N

There are two forces acting on the string. The buoyant force of the ball upward, the tension in the string downward, and the mass of the ball. Since the ball is stationary, these forces must cancel. Thus, T + w = B, which implies:

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Correct Answer: A. 10^-5

Therefore:

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Correct Answer: C. 10 mi*h^-1*s^-1

The formula for acceleration is velocity divided by time:

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Correct Answer: C. 6000 N-m

Assuming that the water stream is tangent to the wheel, it will be perpendicular to the radius vector at the point of contact. Therefore, the torque of the force of the water stream is Torque = r*F = (20m)(300 N) = 6000 N-m.

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Correct Answer: A. N decreases as x increases, but not proportionally.

The normal force is the force that pushes up against on object. For an inclined plane, the formula for normal force is N = m*g*cos(x). The mass of the sled and gravity stay the same, so N must decrease as x increases due to the cosine function. Try 30 degrees for x and then 60 degrees for x in a calculator, you’ll see that the normal force decreases, but does not decrease by a factor of 2.

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