Đề ôn thi Đề thi vào lớp 10 Trường Phổ thông Năng khiếu môn Tiếng Anh - Mã đề PTNK-174

Have you ever wondered how a simple axe can split a thick log of wood into two pieces? The answer lies in one of the six classical simple machines: the wedge. A wedge is essentially two inclined planes joined together to form a sharp edge. This simple tool is designed to separate two objects, or portions of an object, by applying force. It’s a fundamental concept in engineering that we see in many everyday items.

The magic of the wedge works by converting a force applied to its wide end into much larger forces perpendicular to its inclined surfaces. When you strike an axe, (21) __________ force travels down to the sharp edge. This concentrates all the pressure onto a very small area. As a result, the wood cannot resist this immense pressure and begins to split apart. The sharper and thinner the wedge, the less effort is needed to do the work.

A common example that doesn't involve cutting is the doorstop. A doorstop is a wedge used (22) __________ a door open or prevent it from moving. When you push a doorstop under a door, friction is created between the door, the floor, and the wedge itself. This friction (23) __________ and creates a strong holding force. Unlike an axe, its primary purpose isn't to separate things permanently, but to hold them securely in place.

An engineer once explained that a wedge's effectiveness (24) __________ on its angle. He said that a sharper, narrower angle requires less input force, which really hits the nail on the head when you're designing tools for efficiency. From the sharp point of a nail to the thin blade of a knife, the principle is the same: the angle determines the mechanical advantage you get from the tool.

Understanding this principle allows for better tool design. For example, if a doorstop were wider, it would require more force to push it into place, but it might hold the door more firmly once there. This trade-off between ease of use and holding power is a key consideration for engineers. Wedges are simple, yet powerful, demonstrating how basic physics can be used to accomplish great tasks.

For many first-time travelers, the sheer scale and complexity of a modern international airport can be an intimidating experience. Far from being simple transit points, these bustling hubs are often likened to miniature cities, each with its own intricate network of terminals, concourses, and gates. The initial excitement of a journey can quickly turn into apprehension when confronted with thousands of people, diverse signs, and an omnipresent hum of activity. This initial encounter with the organized chaos of an airport often feels like the traveler's first significant hurdle. [I]

Navigating an airport successfully demands more than just finding your way. [II] From the initial check-in counter for luggage drop-off, to the often-stressful security checkpoints with meticulous screening, every step requires attention. Locating your specific departure gate, often amidst a labyrinth of shops and eateries, further tests a traveler's resolve. Understanding boarding calls, currency exchanges, and sometimes language barriers adds layers to this complex challenge.

This global challenge resonates strongly with Vietnamese travelers, especially those embarking on their first international adventures. Vietnam's primary gateways, Noi Bai International Airport in Hanoi and Tan Son Nhat International Airport in Ho Chi Minh City, are incredibly busy and complex hubs. For millions of Vietnamese citizens, successfully maneuvering through these often-crowded facilities is the very first tangible part of any journey abroad. A smooth departure from these environments sets the tone for the entire trip, whether for education, work, or leisure. [III]

For a 14 to 15-year-old, navigating a large airport independently can seem immense. Imagine flying alone for the first time – perhaps to study abroad, visit relatives, or embark on a long-awaited vacation. [IV] This experience, while thrilling, presents a unique test of self-reliance. Knowing the steps, from online check-in and baggage rules to security and finding your gate on time, transforms a stressful ordeal into an empowering achievement. This mastery builds significant confidence, proving a young person's capability to handle responsibilities.

Ultimately, mastering airport navigation is more than just a practical skill; it's a foundational step in becoming an independent and confident global citizen. The initial "lost in the airport" feeling can be overcome with preparation and a clear understanding of the process. Successfully passing through security, locating the correct gate, and finally stepping onto the plane provides a profound sense of accomplishment. It signifies not only the start of a new journey but also a personal milestone, equipping travelers of all ages with the confidence to explore the world.