Sound — Science STD 9 — Question

In which of the following case the work done by a force will be maximum: when the angle between the direction of force and direction of motion is 0^° or 90^°?

Name the following:

1. Seed borne disease.
2. Air borne disease.

Name the device or machines which convert:
Chemical energy into electrical energy.

Calculate:
The number of atoms in 11.5g of Na. [atomic mass: Na = 23u; S = 32u, O = 16u, N = 6.022 × 1023mol^-1]

What is the name of the process due to which dry ice changes into carbon dioxide gas?

Name one crop which can tolerate water logging in the fields and one which cannot.

Name the physical quantity whose unit is watt.

Name two units of power bigger than watt.