If we place our ar at the end of a long pipe and ask our friend to hammer at the other end,we will hear two distinct type of sound.Explain why?

Two charged conducting spheres of radii a and b are connected to each other by a wire. What is the ratio of electric fields at the surfaces of the two spheres? Use the result obtained to explain why charge density on the sharp and pointed ends of a conductor is higher than on its flatter portions.

A long rod made of soft iron is fixed in a vertical position. If a strong magnet A is brought into contact with its upper end, as shown in Fig., then the rod becomes so strongly magnetised that its lower end can support several small objects. If the same magnet is brought in contact with the side of the rod, quite close to the lower end (Fig,), then there is no such strong magnetisation, and the same objects cannot be supported at the lower end of the rod. Explain why magnet A acts differently in the two cases.

When we enter some dark room then for some time we are not able to see anything and rKHOaning there for long,if suddenly strong light is switched on then our eyes can not see anything why?

According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the roadside, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.