Explain the following

1. Why is one end of drawing board pin broad and that, whereas its other end is pointed and staip.
2. Why is the edge of knife kept sharp?
3. Why do the army tanks move over the wide steel chain rather than on the wheels?
4. Why is the foundation of a building made very wide, as compared to its walls?
5. Why are long skis used for gliding over snow?
6. Why does a camel easily cross the desert but not a horse?
7. Why are double tyres provided at the rear wheels of atruck?
8. Why does a sharp nail easily penetrate wood, but not a blunt nail?

2-

We know that Pressure is inversely proportional to area.

So, smaller area will exert more pressure, thus a sharp knife has small area that comes in contact with the object, so more pressure can be applied on the object. Whereas a blunt knife has more area than a sharp knife and the pressure exerted by the blunt knife will be less as compared to that of a sharp knife.

Therefore it becomes easy to cut objects with a sharp knife than a blunt knife and so the edge of knife kept sharp.

3-

We know that,

Pressure = Force / Area.

Area of the wide steel chain is large. So, the pressure acting on the surface is less and the tank moves on the surface easily.