It is difficult to carry a heavy shopping bag with thin handles by hand, but slightly easier when the handles

Question

It is difficult to carry a heavy shopping bag with thin handles by hand, but slightly easier when the handles are covered with a thick piece of cloth. What is the reason behind that?

Examoogle · Accepted Answer

The correct answer is Option C: Increase in surface area reduces the force exerted. The pressure exerted on the hand is inversely proportional to the area of contact. By using a thick piece of cloth, the contact area increases, which decreases the pressure applied to the skin, making it more comfortable to carry.

Step-by-Step Solution & Concepts:
The pressure exerted on the hand is inversely proportional to the area of contact. By using a thick piece of cloth, the contact area increases, which decreases the pressure applied to the skin, making it more comfortable to carry.

Working Principle: According to the definition of pressure $P = \frac{F}{A}$, where $F$ is the force applied and $A$ is the area over which it is distributed. Since the weight of the bag remains constant, increasing the surface area $A$ through the use of a thick cloth results in a significant reduction in the pressure $P$ experienced by the hand.

Key Formulas: $P = \frac{F}{A}$ — Where $P$ is pressure, $F$ is force, and $A$ is surface area.

Key Points: Force and Pressure are directly proportional when Area is constant.; Pressure and Area are inversely proportional when Force is constant.; The SI unit of pressure is the Pascal ($	ext{Pa}$), which is defined as $	ext{N/m}^2$.

Advantages: Reduces localized pain in palm; Prevents skin indentation or bruising

Applications: Wide straps on heavy school bags; Sharp knives are sharpened to decrease edge area for high pressure

Additional Info: Option A is incorrect because adding a cloth does not change the physical tensile strength of the bag handles.. Option B is irrelevant as color does not affect physical forces.. Option D is incorrect as the cloth does not prevent the bag material itself from tearing if the load exceeds its structural limit.

Answer: C is correct — Increasing the surface area decreases the pressure exerted by the handles on the hand, making it less painful to carry.

Exam Tip: In competitive exams, remember that whenever you see 'sharp', 'thin', or 'pointed' objects, it implies a small area leading to high pressure; conversely, 'wide', 'broad', or 'flat' objects are used to reduce pressure.

Examoogle · Answer

Option A: Handles become stronger

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Option B: Cloth is colourful

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Option D: Chances of tearing are eliminated

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