A body falls towards earth in air. Will its total mechanical energy be conserved during the fall? Justify.

Answer carefully, with reasons :-In an elastic collision of two billiard balls, is the total kinetic energy conserved during the short time of collision of the balls (i.e. when they are in contact) ?

If no external torque acts on a body. will its angular velocity remain conserved?

Does total energy remain conserved in the phenomenon of interference ?

A ballon filled with helium rises against gravity increasing its potential energy. the speed of the ballon also increases as it rises. How do you reconcile this with the law of conservation of mechanical energy ? You can neglect viscous drag of air and assume that density of air constant.

A body is falling freely under the action of gravity alone in vacuum. Which of the following quantities remain constant during the fall?