Question

6. A man starting from rest accelerated his automobile and achieved a velocity of 60 m/s in
10 seconds. After that he applies brake and the velocity decreases to 10 m/s in 1 second.
Calculate the acceleration in both the cases.​

Answer 1

• The rate of change of velocity is called acceleration. Its symbol is a.

Now, in first case ,

→ u = 0 m/s

→ v= 60 m/s

→t= 10 sec

→ a = ??

As we know,

$\longrightarrow \: \tt{ a = \frac{v - u}{t} } \\ \\ \rm{putting \: the \: values} \\ \\ \longrightarrow \: \tt{a = \frac{60 - 0}{10} } \\ \\ \longrightarrow \: \tt{ a = \frac{ \cancel{60}}{ \cancel{10} }} \\ \\ \longrightarrow \: \bf{ a = 6 \: ms {}^{ - 2} }$

Now, similarly in the second case;

→ u= 60 m/s

→ v = 10 m/s

→ t= 1 s

$\ \: \tt{a = \frac{10 - 60}{1} } \\ \\ \longrightarrow \: \tt{ a = \frac{ - 50}{1} } \\ \\ \longrightarrow \: \bf{ a = - 50 \: ms {}^{ - 2} }$