Andhra Pradesh Board Class 9 Physics/Chemistry Chapter 9 - Work and EnergyShare
Andhra Pradesh Board Class 9 Physics/Chemistry Chapter 9 - Work and Energy
Identify the wrong statement among the following. Rewrite them by making necessary corrections.
a) Work and energy have different units.
b) When an aero plane takes off, the work done by its weight is positive.
c) The potential energy of spring increases when it is extended and decreases when it is compressed.
d) If the work done by external forces on a system is negative then the energy of the system decreases.
e) When a body is falling freely from a height, its kinetic energy remains constant.
f) The unit of power is watt.
In which of the following cases is the work done positive or zero or negative?
a) Work done by the porter on a suitcase in lifting it from the platform on to his head.
b) Work done by the force of gravity on suitcase as the suitcase falls from porter’s head.
c) Work done by the porter standing on platform with suitcase on his head.
d) Work done by force of gravity on a ball thrown up vertically up into the sky.
e) Work done by force applied by hands of a man swimming in a pond.