Question

www
5. A train accelerates uniformly from 36km/h to 72kmh in 20s Find its acceleration​

Answer 1

Given :-

Initial velocity of train (u) = 36km/h

Final velocity of train (v) =72km/h

Time taken by train (t) = 20 seconds

To find :-

We have to find the acceleration

Formula used !

$\boxed{\textsf{\textbf{\dag\ \ v=u+at}}}$

• First convert it into m/s

$\sf 1\ km/h = \dfrac{1}{18}\ m/s\\ \\ \bullet\sf \cancel{36}\times \dfrac{5}{\cancel{18}}\\ \\ \longrightarrow\sf u= 5\times 2= 10m/s\\ \\ \bullet\sf \cancel{72}\times \dfrac{5}{\cancel{18}}\\ \\ \longrightarrow\sf v= 5\times 4= 20m/s$

• Now find the acceleration
• By putting the value in formula

$\longrightarrow\sf v=u+at\\ \\ \longrightarrow\sf 20= 10+a\times20\\ \\ \longrightarrow\sf 20-10= 20a\\ \\ \longrightarrow\sf 10= 20a\\ \\ \longrightarrow\sf \cancel{\dfrac{10}{20}}=a\\ \\ \longrightarrow\sf \dfrac{1}{2}=a\\ \\ \longrightarrow\sf \ \ or \ a= 0.5m/s^2$

$\boxed{\textsf{\textbf{ Acceleration=0.5m/s}}^2}$