Question

The fuel efficiency of most vehicles traveling at speeds greater than 50 miles per hour ___________ as the vehicle's speed increases, due to the increased aerodynamic drag placed on the vehicle. a. equalizes b. adapts c. stabilizes d. diminishes e. increases f. wanes

Short answer

The correct answer is d. 'diminishes'. As the speed of a vehicle increases beyond 50 miles per hour, the fuel efficiency diminishes due to increased aerodynamic drag.

Step-by-step solution

Understanding the Effect of Speed on Fuel Efficiency

Fuel efficiency means how much distance a vehicle can travel per unit of fuel. At high speeds, the aerodynamic drag increases. This means the vehicle needs more power, thus uses more fuel, to maintain the same speed, hence decreasing the fuel efficiency.

Analyzing the Options

Looking at the options provided, we need to find an option that suggests that the fuel efficiency reduces when the speed is above 50 miles per hour. Option d. 'diminishes', and option f. 'wanes' both suggest a reduction in efficiency.

Choosing the Best Answer

Both 'diminishes' and 'wanes' could technically describe a decrease in efficiency, but the word 'wanes' is more commonly associated with phases or states that come and go, like the moon, rather than steady values like speed and efficiency. Thus, option d. 'diminishes' is the better answer as it more directly suggests a steady decrease.

Key concepts

Fuel Efficiency

Fuel efficiency relates to how effectively a vehicle uses fuel to travel a certain distance. It's typically measured in miles per gallon (MPG) or kilometers per liter (kpl), and it's crucial for determining a vehicle's environmental impact and operational cost. The goal is to maximize fuel efficiency, ensuring a vehicle travels as far as possible with the least amount of fuel.

Several factors impact fuel efficiency:

• Engine type and size: More powerful engines can consume more fuel.
• Vehicle weight: Heavier vehicles require more energy to move.
• Driving habits: Sudden accelerations and braking can reduce efficiency.
• Tire type and condition: Improperly inflated or worn tires can increase fuel consumption.
• Aerodynamic design: More streamlined vehicles face less air resistance.

This leads us to our next topic, which is significant for understanding the exercise: aerodynamic drag.

Aerodynamic Drag

Aerodynamic drag is the resistance a vehicle faces from the air as it travels. Think of it as how hard the air pushes back against a moving car. The faster a vehicle goes, the stronger the aerodynamic drag it experiences. This is because the air molecules are striking the vehicle's surface with greater force and frequency.

Aerodynamic drag increases with speed due to:

• Velocity squared relationship: As speed doubles, drag quadruples.
• Vehicle shape: A boxy shape creates more drag than a sleek, streamlined design.
• Surface area: More area facing the wind creates more resistance.

Higher drag means that a vehicle’s engine works harder to keep moving, which can decrease fuel efficiency. Balance is key: cars are designed to minimize drag for better fuel economy.

Speed and Fuel Consumption

The relationship between speed and fuel consumption is a critical factor in determining fuel efficiency. As speed increases beyond a certain threshold (in many cases, 50 miles per hour), fuel consumption often rises disproportionately due to increased aerodynamic drag.

Key points to consider:

• Optimal speed range: Most vehicles have an ideal speed window for maximum fuel efficiency, often between 30-50 mph.
• Fuel consumption rate: At speeds over this window, engines consume more fuel quickly due to higher resistance.
• Journey planning: Understanding this relationship helps drivers make informed decisions on speed to save fuel and reduce costs.

Recognizing these dynamics allows for better energy management while driving, promoting both economic and environmental benefits.

Vocabulary Skills

The exercise emphasizes understanding key vocabulary related to fuel efficiency and performance. Improving vocabulary skills aids in grasping the concepts more clearly and making better decisions when necessary.

Here are some strategies to enhance vocabulary skills:

• Context clues: Determine the word meaning based on the surrounding text.
• Synonyms and antonyms: Knowing similar and opposite words helps solidify understanding.
• Practice: Regular reading and engagement with varied texts build word knowledge.
• Usage examples: Applying new words in sentences enhances comprehension and recall.

For this problem, understanding words like 'diminishes' and 'wanes' and their contextual usage directly influences selecting the correct answer.

Critical Reasoning

Critical reasoning involves analyzing information and making judgments based on evidence. In GRE problem-solving, critical reasoning plays a vital role in interpreting questions and choosing solutions, especially when options appear similar.

Strategies for improving critical reasoning:

• Question analysis: Carefully read and determine what is being asked.
• Eliminating wrong options: Remove choices that clearly do not fit the criteria.
• Evidential support: Select the option best supported by the information given.
• Reflective thinking: Consider the implications and consequences of each option.

This skill set is crucial in exercises like this one, where discerning differences, such as between 'diminishes' and 'wanes', requires careful thought.