Question

The velocity of train increases uniformly from $20km/h$ to $60km/h$ in $4$ hours. The distance travelled by the train during this period is

• A. 160 km
• B. 180 km
• C. 100 km
• D. 120 km

Answer 1

Answer: (A)

Initial velocity $(u)=20km/h$;
Final velocity $(v)$ $=60km/h$ and time $(t)=4$ hours.
velocity $(v)=60=u+at=20+(a\times 4)$
or, $a=\frac{60-20}{4}=10km/h^2$.
Therefore distance travelled in $4$ hours is $s$
$s=ut+\frac{1}{2}a{t}^2=(20\times 4)+\frac{1}{2}\times 10\times (4{)}^2=160km$.