what force acts perpendicular to the surface of the object in contact with?a. applied b. gravitational. c.normal d. tension.

Normal force.

Explanation:

The normal force is the force that surfaces exert to prevent solid objects from passing through each other. Normal force is a contact force. If two surfaces are not in contact, they can't exert a normal force on each other. It is also perpendicular to the surface of the object in contact with.

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