HESI A2 Physics

Correct Answer: A

Rationale: To determine the velocity of a wave, you need to use the formula v = fλ, where v is the velocity, f is the frequency, and λ is the wavelength. By multiplying the frequency by the wavelength (option A), you are essentially applying the correct formula for calculating wave velocity. This is because the velocity of a wave is directly proportional to both its frequency and wavelength. Option B (adding the frequency and wavelength) and Option C (subtracting the wavelength from the frequency) do not align with the correct formula for wave velocity calculation, as it involves multiplication rather than addition or subtraction. Option D (dividing the wavelength by the frequency) is also incorrect because the correct operation for determining wave velocity is multiplication, not division.

Correct Answer: C

Rationale: To find the image distance using the mirror formula (1/f = 1/v + 1/u), we first need to calculate the object distance (u). Given the object distance (u) is 20 cm, and the focal length (f) is 10 cm, we can substitute these values into the formula to find the image distance (v). Solving for v, we get v = 60 cm. Therefore, the correct answer is C: 60 cm. Choice A (20 cm) is incorrect as the image distance is not equal to the object distance when using a concave mirror. Choice B (40 cm) is incorrect as it does not account for the focal length of the mirror. Choice D (75 cm) is incorrect as it is not the result of the correct calculation using the mirror formula.

Correct Answer: A

Rationale: To determine the velocity of a wave, you need to use the formula v = fλ, where v is the velocity, f is the frequency, and λ is the wavelength. By multiplying the frequency by the wavelength (option A), you are essentially applying the correct formula for calculating wave velocity. This is because the velocity of a wave is directly proportional to both its frequency and wavelength. Option B (adding the frequency and wavelength) and Option C (subtracting the wavelength from the frequency) do not align with the correct formula for wave velocity calculation, as it involves multiplication rather than addition or subtraction. Option D (dividing the wavelength by the frequency) is also incorrect because the correct operation for determining wave velocity is multiplication, not division.

Correct Answer: D

Rationale: The correct answer is D: Strongly repulsive. When two identical positively charged spheres are brought close together, they will experience a strong repulsive force due to like charges repelling each other based on Coulomb's Law. The force between them is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. The repulsive force will increase as the spheres get closer, leading to a strong repulsion. Choices A and C are incorrect because like charges do not attract each other. Choice B is incorrect as the spheres will experience a repulsive force, not a zero force.

Correct Answer: B

Rationale: To find the frequency, we use the formula: speed = wavelength x frequency. Given speed = 12 m/s and wavelength = 2 m, we can rearrange the formula to solve for frequency: frequency = speed / wavelength = 12 m/s / 2 m = 6 Hz. Choice A (38.4 Hz) is incorrect as it would be the frequency if the wavelength was 0.3125 m, not 2 m. Choice C (4.6 Hz) and D (3.75 Hz) are also incorrect as they do not match the calculated frequency of 6 Hz based on the given values.