Physics
It is easier to roll a barrel full of coal tar than to pull it because

more surface area of the barrel is in contact with the road when it is pulled
the rolling friction is much less than the sliding friction
the full weight of the barrel comes into play when it is pulled
coal tar is a liquid and it flows in the barrel when it is rolled

ANSWER DOWNLOAD EXAMIANS APP

Physics
Mirage is due to:

Magnetic disturbances in the atmosphere
Unequal heating of different parts of the atmosphere
Depletion of ozone layer in the atmosphere
Equal heating of different parts of the atmosphere

ANSWER DOWNLOAD EXAMIANS APP