Question

Identify the correct statements from the following :
a) The collisions between the nuclei and fundamental particles are considered as elastic collisions.
b) Emission of an alpha particle by $U^{235}$ is an "elastic collision".
c) The collision between two ivory balls is considered as " elastic collision".
d) A running man jumps into a train. It is an "elastic collision".

• A. Only a & b are true
• B. Only b & c are true
• C. a, b & c are true
• D. b, c & d are true

Answer 1

The correct option is C a, b & c are true

A collision is considered elastic collision if the kinetic energy before collision is equal to the kinetic energy after collision.
In collision of nuclei and fundamental particles, unless there is emission of gamma rays, kinetic energy of the system remains constant.
In Alpha particle emission, energy is not being released in any other form. Hence kinetic energy of the system will remain same before and after the emission.
In collision of two ivory balls, the balls being extremely hard, no deformation happens and for most practical purposes energy is assumed to not being converted into any other form such as heat(which happens when there is friction or deformation).
In the case of a running man jumping on to the train, friction and deformation happens in order for the man to continue moving along with the train. Thus energy was converted into other forms. Hence, it is an example of inelastic.