Correct Answer: D

Rationale: When Jack stands in front of a plane mirror, his image appears the same distance behind the mirror as Jack is in front of it.
Therefore, if Jack is 5 feet away from the mirror, his image will also appear 5 feet behind the mirror. The total distance from Jack to his image is the sum of these distances, which equals 10 feet.

Choices A, B, and C are incorrect because the image distance is not half of the total distance but the same as the object's distance from the mirror.

Correct Answer: A

Rationale: When a dielectric material is inserted between the plates of a charged capacitor, the capacitance will increase. This is because the presence of a dielectric material reduces the electric field between the plates, allowing more charge to be stored for a given voltage, thus increasing the capacitance.
Choice B is incorrect because adding a dielectric material increases capacitance.
Choice C is incorrect because capacitance changes when a dielectric is added.
Choice D is incorrect because the effect of a dielectric on capacitance is predictable.

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.

Correct Answer: C

Rationale: The gravitational force between two objects is inversely proportional to the square of the distance between them. When the distance is halved, the new force of attraction will be 12 units x (1/(0.5)^2) = 12 units x 4 = 24 units.
Therefore, the correct answer is C.
Choice A and B are incorrect as they do not consider the inverse square law of gravitational force.
Choice D is incorrect as reducing the distance between the objects does not lead to a squared increase in force.

Correct Answer: D

Rationale: The momentum of an object is calculated by multiplying its mass by its velocity. In this case, the mass of the ball is 5 kg and its velocity is 5 m/s.
Therefore, the momentum of the ball is 5 kg 5 m/s = 25 kgâ‹…m/s.
Choice A (10 kgâ‹…m/s) is incorrect as it does not account for both mass and velocity.
Choice B (16.2 km/h) is incorrect as it provides a speed in a different unit without considering mass.
Choice C (24.75 kgâ‹…m/s) is incorrect as it does not correctly calculate the momentum based on the given mass and velocity.