Nokea
Ocean waves build during a storm until there is a vertical distance from the high point to the low point of 6 meters and a horizontal distance of 9 meters between adjacent crests. The waves hit the shore every 5 seconds. What is the speed of the waves?
- A. 1.2 m/s
- B. 1.8 m/s
- C. 2.0 m/s
- D. 2.4 m/s
Correct Answer: B
Rationale: To find the speed of the waves, we use the formula: speed = wavelength / period. The wavelength is the horizontal distance between adjacent crests, which is 9 meters in this case. The period is the time it takes for one wave to pass a fixed point, given as 5 seconds. Therefore, speed = 9 meters / 5 seconds = 1.8 m/s. Choice A (1.2 m/s) is incorrect because it miscalculates the speed. Choice C (2.0 m/s) and Choice D (2.4 m/s) are incorrect as they do not correctly calculate the speed using the provided data.
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Which conclusion can be drawn from Ohm's law?
- A. Voltage and current are inversely proportional when resistance is constant.
- B. The ratio of the potential difference between the ends of a conductor to current is a constant, R.
- C. Voltage is the amount of charge that passes through a point per second.
- D. Power (P) can be calculated by multiplying current (I) by voltage (V).
Correct Answer: B
Rationale: Ohm's law states that the ratio of the potential difference (voltage) between the ends of a conductor to the current flowing through it is a constant. Mathematically, this is represented as V = I x R, where V is voltage, I is current, and R is the constant resistance. Therefore, the correct conclusion that can be drawn from Ohm's law is that the ratio of the potential difference between the ends of a conductor to current is a constant, denoted as R. This relationship is fundamental to understanding the behavior of electrical circuits and the effect of resistance on voltage and current. Choice A is incorrect because Ohm's law actually states that voltage and current are directly proportional when resistance is constant. Choice C is incorrect because voltage is not the amount of charge that passes through a point per second; rather, it is the electric potential energy per unit charge. Choice D is incorrect because although power (P) can be calculated by multiplying current (I) by voltage (V), this is not a conclusion directly drawn from Ohm's law.
When a crane hoists a massive object at a constant velocity compared to lifting the same object gradually, the work done by the crane is:
- A. Less
- B. More
- C. Identical
- D. Dependent on the object's mass
Correct Answer: C
Rationale: The work done by the crane is identical in both scenarios. Work is defined as the force applied over a distance. Since the force needed to lift the object is equal to its weight and the displacement is the same, the work done is identical, whether the object is lifted gradually or at a constant velocity. Choice A is incorrect because the work done is the same in both cases. Choice B is incorrect as well since the work done does not increase. Choice D is incorrect as the mass of the object does not affect the work done by the crane in this scenario.
Faraday's law of electromagnetic induction states that a changing magnetic field in a conductor induces a/an:
- A. Increase in resistance
- B. Electromotive force
- C. Static electric charge
- D. Decrease in capacitance
Correct Answer: B
Rationale: Faraday's law of electromagnetic induction states that a changing magnetic field induces an electromotive force in a conductor. This electromotive force is responsible for generating electricity in power plants and various electrical devices. The induced current is a result of the changing magnetic field, not an increase in resistance (choice A), static electric charge (choice C), or a decrease in capacitance (choice D). Hence, the correct answer is B.
A 110-volt appliance draws 0 amperes. How many watts of power does it require?
- A. 0 watts
- B. 108 watts
- C. 112 watts
- D. 220 watts
Correct Answer: A
Rationale: When a 110-volt appliance draws 0 amperes, it means that the power consumption is zero as well. The formula to calculate power is P = V x I, where P is power in watts, V is voltage in volts, and I is current in amperes. Since the current is 0 amperes, the power required by the appliance is also 0 watts. Therefore, the correct answer is 0 watts. Choice B, 108 watts, is incorrect because there is no current drawn. Choice C, 112 watts, and choice D, 220 watts, are incorrect as well since the appliance is not consuming any power when drawing 0 amperes.
According to Bernoulli's principle, when the flow velocity (v) of an incompressible fluid increases in a constricted pipe, the pressure (P) will:
- A. Depend on the specific fluid type
- B. Decrease
- C. Remain constant
- D. Increase
Correct Answer: B
Rationale: Bernoulli's principle states that in a constricted pipe with increasing flow velocity of an incompressible fluid, the pressure decreases. This is due to the conservation of energy, where the total energy of the fluid (sum of kinetic energy, potential energy, and pressure energy) remains constant along the flow path. As the fluid velocity increases, its kinetic energy increases at the expense of pressure energy, causing a decrease in pressure. Therefore, the correct answer is B. Choices A, C, and D are incorrect. The pressure changes in the system are primarily driven by the fluid velocity and the conservation of energy principle, not by the specific fluid type, which is a constant. The pressure is not constant but decreases with increasing flow velocity due to the energy transformation occurring in the system. Lastly, the pressure does not increase; it decreases as the fluid velocity rises.