4. Velocity ratio is not affected by friction. why?

Explanation:

I am aware that, referring only to low velocities,that the velocity of an object does not greatly affect the friction coefficient ... There the frictional force is proportional to the velocity for small velocities.That proportionality breaks down when the velocity becomes bigger.

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask

think its the third option