Question

A bus starts with an initial speed of 30km/hr and increases its speed by 6km/hr every hour. How long will it take to cover a distance 693km?

Answer 1

here,

distance (s )=693 km

initial speed (u)=30 km/hr

accelerate with 6 km /hr

so,

a=6 km /hr

t=?

s=ut +1/2at^2

693=30t+1/2×6t^2

693=30 t +3t^2

-3t^2+30t+693=0

3 (-t^2+10t+231)=0

-t^2+10t+231=0

after solving this quadratic equation we get value of t

t=-11 and t=21

time is always +ve

so answer is

t=21 hrs