Examkin

Question

Difficulty: EasyFriction and Resistance

Match each mechanical design feature with its primary physical effect on friction or resistance.

  • Applying lubricating oil to metal gear teethDecreases sliding friction by creating a slippery barrier between solid surfaces
  • Installing steel ball bearings around a rotating axleReduces resistance by converting sliding contact into rolling contact
  • Molding deep rubber treads onto an off-road tireIncreases static friction to provide better traction against the ground
  • Shaping an airplane fuselage with a smooth, streamlined noseReduces fluid resistance (aerodynamic drag) caused by moving through air

Answer

Lubricating oil decreases sliding friction, ball bearings convert sliding friction to rolling friction, heavy tire treads increase static friction, and a streamlined aerodynamic shape reduces fluid resistance.
Each feature is a standard engineering method for managing a specific form of resistance based on its application. Lubricants handle sliding friction, bearings manage rotational contact by rolling, treads ensure static friction for grip, and aerodynamics handle fluid resistance in the air.

Step-by-Step Solution

1
Analyze each mechanical design feature to determine what materials or surfaces are interacting.
Gears involve metal-on-metal sliding; axles involve rotational contact; tires interact directly with the ground; airplanes interact with the air.
Identifying the interacting materials reveals the specific type of physical resistance involved in each scenario.
2
Determine whether the design goal of the feature is to increase or decrease the physical resistance.
Tires need increased friction for grip, while gears, axles, and airplanes need decreased resistance for mechanical efficiency.
Matching the design goal (grip vs. efficiency) with the physical mechanism leads to the correct pairings.

Key Concept

Methods of Controlling Friction and Resistance
Rate this question

Topics

Friction and Resistance

More questions from this topic