MCAT Question of the Day

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: A. 10^-5

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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: 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: 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: 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. Electric current will only flow from a high potential to a lower potential.

Electric current moves in the direction positive charges move in. Therefore, the electric flow of current flows from the point of higher potential to lower potential, similar to how water falls from the top of the waterfall to the bottom.

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Correct Answer: C. a = sin 30^o x 9.8 m/s² = 4.9 m/s²

Gravity is calculated from the vertical component of the force on the mass: sin theta = opposite/hypotenuse.

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Correct Answer: D. The kinetic energy increases to 9 times its original value.

Kinetic energy is: KE = (1/2)mv². The kinetic energy is directly proportional to the square of the velocity (or speed). If the speed is multiplied by 3 (tripled), the KE must be multiplied by 3² = 9. Sidenote, race car spelled backwards is still race car.

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Correct Answer: A. Speed = 6.67 m/s and Velocity = zero

Speed is a scalar quantity involving magnitude only: Speed = distance/time = 400/60 = 6.67 m/s. Velocity is a vector quantity involving both magnitude and direction: Velocity = displacement/time = 0/60 = zero.

Distance traveled is not dependent on a direction, but displacement is. Displacement = distance from the finish to the start, which in this case is zero as the athlete has run around an oval to arrive back at her starting place.

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