Question

please solve this math problem

Answer 1

t(1)=1h 30m(time)=> 1.5 h
v(1)=60kmph(speed)
s(1)=? (distance)
=> v=s/t ( one of the equations of motion in physics)
=> s= vt => 60×1.5= 90 km is the distance travelled

now we have to find what is the time taken to cover same distance (90km) at the speed of 45kmph which is
we know
v= 45kmph
s= 90km
t=?

from the equation v=s/t we get t= s/v( by transposing s from RHS to LHS)
t= s/v=> 90/45=> 2

therefore the time taken to travel a distance of 90 km at the speed of 45kmph is 2hours.

Answer 2

Given, initial velocity=60 km/hr.                final velocity=45 km/hr                          & time=1 hr 30 mins=(60+30)mins=90 mins.Since the speed is decreaseing from 60km/ hr to 45km/hr,we 'll find retardation in the place of acceleration                                                        Final velocity = Initial velocity+retardation × time.                              =45=60+a×90mins =60-45=90×a=15=90×a.                                        a=15/90=0.16m/s sq.                                  Time required to cover the distance=final velocity -initial velocity/retardation.                                   =45-60/0.16=25mins