Why is pulling the lawn roller preferred to pushing it ?

(A) : It is easier to pull a lawn roller than to push on the same horizontal rough surface (R ) : Pulling body decreases normal reaction

Which one of the following is preferred to control the acidity? Why?

Explain why (a) a horse cannot pull a cart and run in empty space, (b) passengers are thrown forward from their seats when a speeding bus stops suddenly, (c) it is easier to pull a lawn mower than to push it, (d) a cricketer moves his hands backwards while holding a catch.

Why gaseous fuels are preferred over solid and liquid fuels?