2017 · Q16
A person is standing on a frictionless horizontal ground. How can he move by a certain distance on this ground ?
General KnowledgePhysics
- ABy sneezing
- BBy jumping
- CBy running
- DBy rolling
Explanation
On a frictionless surface no horizontal external force can be obtained from the ground, so jumping, running and rolling — all of which depend on friction between the feet (or body) and the ground — cannot produce motion. By sneezing, the person expels air forward; Newton's third law gives an equal and opposite reaction that pushes the person backward. This is the same reaction principle on which rockets work. Only sneezing can therefore move the person.