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

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

ANSWER DOWNLOAD EXAMIANS APP

Physics
Absolute Zero is defined as

At which liquid Helium boils
The temperature at which all molecular motion ceases
At which the volume becomes zero
At which water boils at 298K

ANSWER DOWNLOAD EXAMIANS APP