Forces and Motion

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Questions and Answers

Consider a scenario involving a spacecraft maneuvering near a supermassive black hole. Given the principles of general relativity and the inverse square law of gravitation, which of the following adjustments to the spacecraft's trajectory would most effectively minimize tidal forces experienced by the spacecraft?

Increasing the spacecraft's albedo to reduce radiative pressure from the accretion disk.
Modulating the spacecraft's trajectory to orbit at the innermost stable circular orbit (ISCO) while utilizing advanced gravitational shielding.
Employing quantum entanglement-based communication to anticipate gravitational anomalies.
Maximizing the spacecraft's proper acceleration while maintaining a constant Schwarzschild radius relative to the black hole. (correct)

A research team is designing a novel triboelectric nanogenerator (TENG) that relies on maximizing static friction at the interface between two dissimilar materials. To optimize the TENG's performance in a high-humidity environment, which of the following surface modification strategies would be most effective in maintaining high static friction?

Creating a hierarchical micro/nanostructured surface with hydrophobic coatings to minimize the contact area with water. (correct)
Introducing a thin film of ionic liquid to enhance interfacial charge transfer and reduce surface energy.
Employing a sacrificial polymer coating that degrades over time, creating a self-roughening effect and increasing real contact area.
Applying a self-assembled monolayer (SAM) of amphiphilic molecules to promote water condensation and capillary bridging.

In the context of computational fluid dynamics (CFD), consider a simulation of airflow around an airfoil at a high Reynolds number. Which turbulence model would most accurately predict the onset of flow separation and the resulting pressure drag due to fluid friction?

The k-epsilon (k-$\epsilon$) model with standard wall functions, given its robustness and wide range of applicability.
The Spalart-Allmaras model, due to its computational efficiency and suitability for attached boundary layers.
The Large Eddy Simulation (LES) model, when combined with a wall-adapting local eddy-viscosity (WALE) subgrid-scale model, to capture near-wall turbulence. (correct)
The Reynolds Stress Model (RSM), owing to its ability to resolve anisotropic turbulence and streamline curvature effects.

Imagine a scenario where a team is developing a magnetic levitation (Maglev) system for high-speed trains. To minimize energy losses due to eddy current damping as the train moves, which strategy is most effective for designing the guideway's electromagnetic properties, assuming a constant train speed and magnetic field strength?

Employing a laminated structure with alternating layers of conductive and insulating materials to reduce the magnitude of induced eddy currents. (B) Signup and view all the answers

Consider a scenario involving the design of a microfluidic device for high-throughput chemical screening. To minimize non-specific protein adsorption on the channel walls, thereby reducing electrical double layer interference, which surface modification technique would be most effective in this scenario?

Grafting poly(ethylene glycol) (PEG) chains onto the channel surface via silanization to create a steric barrier against protein adsorption. (A) Signup and view all the answers

A team of engineers is tasked with designing an ultra-sensitive gravimeter for detecting subtle variations in the Earth's gravitational field caused by deep subsurface geological formations. Which of the following advanced technologies would provide the highest precision and resolution for this application?

An atom interferometer gravimeter employing laser-cooled atoms in a Ramsey-Bordé interferometer to measure the phase shift induced by gravity on the atomic wavefunctions. (A) Signup and view all the answers

Consider a scenario where a spacecraft is orbiting a rapidly rotating neutron star with an intense magnetic field (magnetar). Which relativistic effect would most significantly influence the spacecraft's trajectory and require precise modeling for accurate navigation?

The Lense-Thirring effect (frame-dragging) caused by the neutron star's rotation, resulting in a precession of the spacecraft's orbital plane. (B) Signup and view all the answers

A team is developing a novel haptic feedback system that relies on electrostatic friction modulation to simulate realistic textures on a touchscreen. Which of the following factors would most critically limit the achievable spatial resolution and fidelity of the haptic rendering?

The size and shape of the electrode array used to generate local electrostatic fields, determining the minimum feature size that can be rendered. (B) Signup and view all the answers

Consider a scenario where you are analyzing the frictional behavior of a novel composite material designed for use in high-speed rail braking systems. The material exhibits a complex interplay between adhesion, abrasion, and tribochemical reactions at the contact interface. Which advanced analytical technique would provide the most comprehensive insights into the dominant wear mechanisms and the evolution of the tribological contact?

In-situ Raman spectroscopy to monitor the formation and transformation of tribochemical reaction products at the contact interface during sliding. (B) Signup and view all the answers

Imagine you are tasked with optimizing the performance of a micro-electro-mechanical system (MEMS) gyroscope. Which of the following strategies would most effectively mitigate the impact of Brownian motion on the gyroscope's sensitivity and accuracy?

Increasing the mass of the gyroscope's proof mass to reduce its susceptibility to random thermal forces. (A) Signup and view all the answers

Flashcards

Force Definition

A push or pull on an object.

Contact Force

A force that requires direct contact between objects.