Question

In which one of the following situations is linear momentum not conserved?

1) When two objects collide and stick together
2) When an object is acted upon by an external force
3) When an object is in free fall
4) When an object is at rest

Answer 1

Linear momentum is not conserved when an object is acted upon by an external force, which disrupts the isolated system necessary for momentum conservation.

Step-by-step explanation:

Linear momentum is conserved in several types of collisions, provided that no external forces are acting on the objects involved. However, in the situations provided, linear momentum is not conserved when an object is acted upon by an external force. The conservation of momentum only applies in an isolated system where the net external force is zero.

The other scenarios given, such as two objects colliding and sticking together (inelastic collision), an object in free fall (where gravity is a conservative force that doesn't affect the momentum of the system), or an object at rest (where momentum is initially and finally zero), do not indicate a violation of momentum conservation assuming no additional external forces are at play.