Bags with wide straps are preferred to carry heavy loads. The reason for this is :
- A.Increase in area of contact increases the pressure exerted
- B.Increase in area of contact increases the force exerted
- C.Increase in area of contact reduces pressure exerted
- D.Increase in area of contact reduces the force exerted
Correct answer
Explanation
The correct answer is C, increase in area of contact reduces pressure exerted. Pressure is the force acting on unit area, that is P equals F divided by A, so for the same force a larger area of contact means smaller pressure. The weight of the bag stays exactly the same whether the strap is thin or wide, but a wide strap spreads that weight over more of the shoulder, so the shoulder feels less pressure and the strap does not cut into the skin. The same idea explains why school bags, seat belts and the wide tyres of a tractor are made broad. A is wrong because it states the relation upside down, since pressure falls when area rises. B and D are wrong because the force is simply the weight of the load and the width of the strap cannot change it; only the pressure changes. Exam tip: P equals F divided by A, so broad straps and flat feet reduce pressure while sharp knives and pointed nails increase it.
Practice Questions
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- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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- D.Eyepiece-Objective lens-Body tube-Mirror
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- C.Histones are proteins associated with lipids in the cytosol.
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