ICSE Class 8 Physics
Think and Answer Questions
1. Why do porters place a folded cloth on their heads while carrying heavy loads?
The folded cloth increases the area of contact between the load and the head. A larger area reduces pressure. Therefore, the load feels less painful and more comfortable to carry.
2. Why are school bags provided with broad straps instead of thin straps?
Broad straps increase the area of contact with the shoulders. This reduces pressure and makes the bag easier to carry.
3. Why can a sharp needle pierce cloth easily while a blunt needle cannot?
A sharp needle has a very small area at its tip. Therefore, it produces a large pressure even with a small force and easily pierces the cloth.
4. Why does a person sink more in sand while standing than while lying down?
When standing, the body weight acts on a small area of the feet, producing high pressure. When lying down, the weight is distributed over a larger area, reducing pressure and preventing sinking.
5. Why do tractors have broad tyres?
Broad tyres increase the area of contact with the ground. This reduces pressure and prevents the tractor from sinking into soft soil.
6. Why is it easier to loosen a tight nut using a longer spanner?
A longer spanner increases the perpendicular distance from the pivot. This produces a greater moment of force, making it easier to loosen the nut.
7. Why are dams made thicker at the bottom than at the top?
Water pressure increases with depth. The bottom part of the dam experiences greater pressure, so it is made thicker and stronger to withstand the force.
8. Why do divers experience greater pressure at greater depths in water?
As depth increases, the amount of water above the diver increases. Therefore, water pressure becomes greater.
9. Why do mountaineers find it difficult to breathe at high altitudes?
At high altitudes, atmospheric pressure and the amount of oxygen in the air are lower. Therefore, breathing becomes difficult.
10. Why do we use a knife with a sharp edge for cutting vegetables?
A sharp edge has a smaller area of contact. It produces greater pressure for the same force and cuts vegetables easily.
11. Why do camels walk easily on desert sand while horses struggle?
Camels have broad feet that spread their weight over a larger area. This reduces pressure on the sand and prevents sinking.
12. Why should force be applied perpendicular to a door while opening it?
A perpendicular force produces the maximum moment of force. Therefore, the door opens more easily.
