MCAT Question of the Day

Correct Answer: B. 10 N

What are the forces on the book? The weight, 40 N, and the normal force, N are downward forces, and the only upward force is our 50 N push. Since the bloc k is not accelerating vertically, the net vertical force must be zero. Therefore, 40 + N must be 50, which means N = 10 N.

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Correct Answer: A. 0 N

Since the velocity is constant, the acceleration a is zero, so using F = ma, we know that the net force must be zero as well.

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Correct Answer: C. 141 V.

By definition, Vrms = Vmax / sqrt(2). Therefore, Vmax = sqrt(2)*Vrms = (1.41)(100V) = 141 V.

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Correct Answer: B. 0.5 m.

Once the ninja star comes to rest at the end of the spring, the upward force by the spring must balance the downward force of gravity. That is, kx = mg. Solving for x yields x = mg/k (1)(10)/(20) = 0.5 m.

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Correct Answer: D. The acceleration is not zero and is always directed toward the center of the path.

Choice A is false because the object’s direction of motion is always changing, and choice B is false because the velocity is not constant. The acceleration, termed centripetal, points toward the center of the circular path.

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Correct Answer: B. F

Since the GameCube is totally submerged at both depths, the buoyant force, B = pVg, is the same at both depths.

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Correct Answer: B.

Finitiating= ( us)N ; And Fmaintaining= ( uk)N

Fi– Fm= (us– uk)N = (0.50 – 0.20)(50 N) = 15 N

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Correct Answer: C.

FG earth = G mearthmbody/r^2

On the planet we get:
FG planet = G 9mearthmbody/3r^2 = FG earth
Since the force of gravity and the mass of the astronaut remain the same on both the planet and on earth, the acceleration due to gravity must also be the same, F/m = g = constant.

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Correct Answer: A. greater than the power of either individual lens.

Lens power is the reciprocal of the focal length: P = 1/f. If the effective focal length of the lens combination is less than the focal length of either individual lens, then the power of the combination must be greater than the power of either individual lens.

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Correct Answer: A. 3 m/s

Momentum is conserved. Since both carts come to rest the total momentum must be zero. If the two carts are labeled A and B then:

MaVa = MbVb
Vb = (30 kg)(5 m/s) / 50 kg = 3 m/s.

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