HESI A2 Physics Quizlet

Correct Answer: B

Rationale: The correct answer is B: The speed of light. In Einstein's mass-energy equation (E=mc^2), 'c' represents the speed of light in a vacuum, which is approximately 3 x 10^8 meters per second. This constant is crucial in the equation as it shows the relationship between mass and energy. The speed of light is a fundamental physical constant and plays a significant role in various aspects of physics, including relativity. Incorrect choices: A: Distance in centimeters - Distance in centimeters is not represented by 'c' in Einstein's equation. C: Degrees Celsius - 'c' does not represent temperature in degrees Celsius in the equation. D: Centrifugal force - 'c' does not represent centrifugal force in the equation.

Correct Answer: B

Rationale: The Reynolds number (Re) is used to characterize the flow regime of a fluid, determining if it is laminar or turbulent. It is calculated as the ratio of inertial forces to viscous forces. For low Re, flow is laminar, while for high Re, flow is turbulent. Surface tension (C) and buoyancy force (D) do not directly relate to Re. Fluid density (A) affects the Reynolds number indirectly through viscosity.

Correct Answer: C

Rationale: According to the zeroth law of thermodynamics, two systems are in thermal equilibrium if they have the same temperature. This is because temperature is a measure of the average kinetic energy of particles in a system, and when two systems have the same temperature, there is no net transfer of heat between them. Choice A (same pressure) and B (same volume) are not correct because pressure and volume are not sufficient indicators of thermal equilibrium. Choice D (made of the same material) is also incorrect as different materials can still be in thermal equilibrium if they have the same temperature.

Correct Answer: A

Rationale: The correct answer is A, P = ρgh. This is derived from the hydrostatic equation, which states that pressure in a static fluid at a depth h is directly proportional to the density of the fluid (ρ), gravitational acceleration (g), and depth (h). Therefore, P = ρgh is the correct formula to calculate pressure in a static fluid. Choice B, P = γh, does not include the density of the fluid and is incorrect. Choice C, P = μgh, introduces a new variable μ which is not part of the hydrostatic equation and is thus incorrect. Choice D, P = bh, does not include the density of the fluid or gravitational acceleration, making it an incorrect formula for calculating pressure in a static fluid.

Correct Answer: B

Rationale: The correct answer is B: Ketchup. Ketchup is a common example of a shear-thinning fluid because its viscosity decreases under shear stress. When force is applied to ketchup, its resistance decreases, making it easier to flow. This behavior is characteristic of shear-thinning fluids, where viscosity decreases with increasing shear rate. Water (Choice A) is a Newtonian fluid with constant viscosity, while Air (Choice C) and Alcohol (Choice D) do not exhibit shear-thinning behavior. Therefore, B is the correct choice.