Question

You need to hang a large rectangular picture frame on a wall in an empty room. To ensure that it is vertical (and not tilted), which of the following will help you hang the picture correctly (not tilted)? (No additional items are to be used other than the ones specified in each of the options)

• A. A wooden stick, a cutter and a pencil
• B. A pencil, a compass and a cutter
• C. A flexible and transparent pipe and a mug of water
• D. Some card paper, a steel-ruler and a pair of scissors

Hint:

This type of question tests practical application of basic physics principles. When you see a problem about leveling, think about gravity. The most common tools that use gravity for reference are a plumb line (for vertical lines) and a spirit/water level (for horizontal lines).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The core problem is to ensure a picture frame is hung perfectly level (horizontal) without a standard spirit level. We need to identify which set of tools can be used to create a makeshift device for this purpose. "Vertical" in the question context means the top and bottom edges are horizontal, and the side edges are vertical.
Step 2: Key Formula or Approach:
The key scientific principle to use here is that the surface of a liquid at rest in a uniform gravitational field is always perfectly horizontal. We need to find the option that allows us to utilize this principle.
Step 3: Detailed Explanation:
Let's analyze the options:
- (A) A wooden stick, a cutter and a pencil: These tools can be used for measuring and marking, but they provide no reference for a true horizontal line.
- (B) A pencil, a compass and a cutter: A compass is used for drawing circles or arcs. It cannot determine a horizontal level.
- (C) A flexible and transparent pipe and a mug of water: This is the correct set of tools. By filling the flexible pipe with water from the mug, one can create a simple and effective water level. If you hold the two ends of the pipe up, the water level at each end will be at the exact same height, regardless of the pipe's shape in between. By marking the water level at two points on the wall, you can draw a perfectly horizontal line between them to align the picture frame.
- (D) Some card paper, a steel-ruler and a pair of scissors: These are useful for crafting and measuring, but like option (A), they offer no external reference for what is truly horizontal.
Step 4: Final Answer:
The combination of a flexible pipe and water can be used to create a water level, which is the only method among the options to establish a true horizontal line for hanging the picture frame correctly. This corresponds to option (C).