when a small object floats on the surface of a liquid the surface tension creates a

HESI A2

HESI A2 Physics Quizlet

1. When a small object floats on the surface of a liquid, the surface tension creates a:

A. Buoyant force acting upwards
B. Pressure difference causing sinking
C. Drag force opposing motion
D. Restoring force towards equilibrium

Correct answer: D

Rationale: Surface tension creates a restoring force that holds the object on the surface. The liquid's surface behaves like a stretched membrane, and when disturbed, it tends to return the object to its original position, creating a restoring force. The other choices are incorrect: A buoyant force acts on objects submerged in a fluid, not floating on the surface; pressure differences usually affect sinking objects, not floating ones; drag force is a resistance force that opposes motion, not related to surface tension.

2. An airplane travels 500 miles northeast and then, on the return trip, travels 500 miles southwest. Which of the following is true?

A. The displacement of the plane is 1,000 miles, and the distance traveled is 0 miles.
B. The displacement of the plane is 1,000 miles, and the distance traveled is 1,000 miles.
C. The displacement of the plane is 0 miles, and the distance traveled is 0 miles.
D. The displacement of the plane is 0 miles, and the distance traveled is 1,000 miles.

Correct answer: D

Rationale: The displacement of an object is the change in position from the starting point to the ending point, regardless of the path taken. In this case, the airplane returns to its original position after traveling 500 miles northeast and then 500 miles southwest. Therefore, the displacement is 0 miles. However, the distance traveled is the total path covered, which is 500 miles northeast plus 500 miles southwest, for a total of 1,000 miles. Choice A is incorrect because the displacement is not the sum of the distances traveled. Choice B is incorrect as it incorrectly states that both the displacement and the distance traveled are 1,000 miles. Choice C is incorrect as it states that both the displacement and the distance traveled are 0 miles, which is not the case.

3. Why doesn’t a raindrop accelerate as it approaches the ground?

A. Gravity pulls it down at a constant rate.
B. Air resistance counteracts the gravitational force.
C. Its mass decreases, decreasing its speed.
D. Objects in motion decelerate over distance.

Correct answer: B

Rationale: The correct answer is B. As a raindrop falls, it experiences air resistance which counteracts the gravitational force pulling it down. This balancing of forces prevents the raindrop from accelerating further as it approaches the ground. Choice A is incorrect because while gravity is pulling the raindrop down, air resistance opposes this force. Choice C is incorrect as the mass of the raindrop remains constant during its fall. Choice D is incorrect because objects in motion may decelerate due to various factors, but in this case, the focus is on why the raindrop doesn't accelerate.

4. For the core of an electromagnet, a material with high:

A. Resistivity is ideal
B. Permeability is preferred
C. Permittivity is crucial
D. Dielectric strength is essential

Correct answer: B

Rationale: A material with high permeability is preferred for the core of an electromagnet because it allows magnetic field lines to pass through it easily, enhancing the strength of the magnetic field generated. Choice A is incorrect because high resistivity would impede the flow of current in the coil, reducing the strength of the magnetic field. Choice C is incorrect as permittivity is related to electric fields, not magnetic fields. Choice D is also incorrect because dielectric strength is about insulating materials against breakdown under an electric field, not relevant to enhancing magnetic fields.

5. Fluids can be categorized based on their shear stress-strain rate relationship. An ideal fluid exhibits:

A. Zero shear stress at any strain rate
B. Linear relationship between shear stress and strain rate (Newtonian)
C. Non-linear relationship between shear stress and strain rate (Non-Newtonian)
D. High dependence of viscosity on temperature

Correct answer: A

Rationale: An ideal fluid, often referred to as an inviscid fluid, is a theoretical concept used in fluid mechanics to simplify calculations. It is characterized by having zero shear stress at any strain rate. In reality, such fluids do not exist, but they serve as a useful starting point for understanding fluid behavior in idealized situations. Choice B is incorrect because a linear relationship between shear stress and strain rate defines a Newtonian fluid, not an ideal fluid. Choice C is incorrect because a non-linear relationship between shear stress and strain rate characterizes Non-Newtonian fluids, not ideal fluids. Choice D is incorrect because the high dependence of viscosity on temperature is a characteristic seen in real fluids and does not define an ideal fluid.