Time and Distance

important fomulae

Speed= \(\left(\frac{\text { Distance }}{\text { Time }}\right)\)

Time =\(\left(\frac{\text { Distance }}{\text { Speed }}\right)\)

Distance = (Speed x Time).


Conversions :

conversion of km/hr to m/sec 

\(\mathrm{km} / \mathrm{hr}=\left(x \times \frac{5}{18}\right) \mathrm{m} / \mathrm{sec}\)

conversion of m /sex to km/hr

x  \( \mathrm{m} / \mathrm{sec}=\left(x \times \frac{18}{5}\right) \mathrm{km} / \mathrm{hr}\).

remember points

  1. If the ratio of the speeds of A and B is a : b, then the ratio of the times taken by then to cover the same distance is   \(\frac{1}{a}: \frac{1}{b}\) or b: a.
  2. Suppose a man covers a certain distance at x \(\frac {km}{hr}\) and an equal distance at y km /hr . Then the average speed during the whole journey is \(\left(\frac{2 x y}{x+y}\right) \mathrm{km} / \mathrm{hr}\).