Material that is not attracted to metal
A. True
if cold air is replacing warm air it is a cold front and vice versa.
The unmagnetized pieces of iron would be randomly pointing to directions, this is true because although influenced with the magnetic domain, the direction of the unmagnetized iron field of attraction is not uniform or does not have preferred direction.
A scalar is something that only has speed without a DIRECTION while a vector has direction. acceleration is a vector and mass is a scalar.
This can be seen as a trick question because heat engines can typically never be 100 percent efficient. This is due to the presence of inefficiencies such as friction and heat loss to the environment. Even the best heat engines can only go up to around 50% efficiency.