9. A motor car starts with the speed of 70km/hr with itsspeed increasi

1.	9. A motor car starts with the speed of 70km/hr with itsspeed increasing every two hours by 10 kmph. In howmany hours will it cover 345 kms? Ans 9/2 hrUCEED IJEE.J
Answer» The acceleration of motor car is. = 10/2 = 5km/hr² now using , newtons 2nd equation S =ut + 1/2at²=> 345 = 70t +1/25t²=> 5t²+140t-690 = 0=> t²+28t-138 = 0=> t = [-28±√(28²+4*138)]/2=> t = (-28+26.8)/2 = 8.8/2 ≈ 9/2 hrs can u plz explain me as a aptitude student not like a science student plz you have to use this.. equation.. because speed will always.. vary here.. we can't use any direct aptitude , and basic science is also aptitude..👍 ok thanx

9. A motor car starts with the speed of 70km/hr with itsspeed increasing every two hours by 10 kmph. In howmany hours will it cover 345 kms? Ans 9/2 hrUCEED IJEE.J

Answer»

The acceleration of motor car is. = 10/2 = 5km/hr²

now using , newtons 2nd equation

S =ut + 1/2*at²=> 345 = 70*t +1/2*5*t²=> 5t²+140t-690 = 0=> t²+28t-138 = 0=> t = [-28±√(28²+4*138)]/2=> t = (-28+26.8)/2 = 8.8/2 ≈ 9/2 hrs

can u plz explain me as a aptitude student not like a science student plz

you have to use this.. equation.. because speed will always.. vary here.. we can't use any direct aptitude ,

and basic science is also aptitude..👍

ok thanx