When a ball m is thrown upwards to a height h, the work done by the force of gravity is:

1. mgh
2. -mgh
3. mg
4. mgh²

A coolie A takes 1 minute to lift a load to the roof of a bus whereas coolie B take 2 minutes to lift the same load to the roof of the same bus. The work done by B is:

1. equal to work done by A
2. greater than work done by A
3. less than work done by A
4. none of the above.

1 Joule is equivalent to …………… erg

1. 10⁵
2. 10⁷
3. 10⁹
4. 1

The energy of electron is 2.5 eV. When expressed in Joule, it is

1. 1.6 x 10^-19 J
2. 4.0 x 10^-19 J
3. 3.2 x 10^-19 J
4. 0