Can kinetic energy of a system be increased without applying any external force on the system?

Can K.E. of a system be increased or decreased without applying any external force on the system?

If no external force acts on a system

Change in kinetic energy of the system is equal to

A disc can roll wihtout slippingg, without applying any external force on a

Assertion : Net external force acting on a system of particles is zero but it possible that kinetic energy of the system increases . Reason : Kinetic energy of the system can be changed by internal forces of the system .

The potential energy of a system increased if work is done

(a) Can kinetic energy of a system be changed without changing its momentum ? (b) Can momentum of a system be changed without changing its kinetic energy?

Statement -1: If kinetic energy of a system is zero then linear momentum of each of particle of the system must be zero. Statement-2: If linear momentum of a system is zero then kinetic energy of system must be zero. Statement-3: If linear momentum of a particle is zero then kinetic energy is zero. Select the correct sequence.

Statement 1: Two spheres undergo a perfectly elastic collision. The kinetic energy of system of both spheres is always constant. [There is no external force on system of both spheres]. Statement 2: If net external force on a system is zero, the velocity of centre of mass remains constant.