Physics
Water pipes in hilly areas often burst on a cold frosty night, because

Water in the pipes freezes and on freezing water expands, so pipes break
None of these
Frost makes the pipes rusty, so they break
The material of which pipes are made contracts due to cold and so breaks

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

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
the rolling friction is much less than the sliding friction
more surface area of the barrel is in contact with the road when it is pulled

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