Two identical particles move towards each other with velocity $$2v$$ and $$v$$ respectively. The velocity of center of mass is

A particle of mass $$m$$ moves along line PC with velocity $$v$$ as shown. What is the angular momentum of the particle about P?

Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside will

Two spheres of the same material have radii $$1$$ $$m$$ and $$4$$ $$m$$ and temperatures $$4000$$ $$K$$ and $$2000$$ $$K$$ respectively. The ratio of the energy radiated per second by the first sphere to that by the second is