Question

Solve 1 question as fast as possible
with detailed explanation

Answer 1

we have used the two equations V is equal to you + 80 and S is equal to UT plus half a t square

Answer 2

time ratio =1:8:1

let say rational constant = x

Let it accelerates with say a in time 'x'

then it reaches a velocity 'v'and continues motion for '8x' time

and finally then retards with 'b' in time 'x'.

v = u + at

v=0+ax

v=ax

60=ax

a=60/x


and, 0=v-bx

b=60/x


Distance covered in the time of acceleration,

S = ut + 1/2at^2

S1=0+1/2at^2

S1=1/2ax^2 = 1/2 * 60/x * x^2 = 30x


Distance covered while moving with constant velocity is,

S2= vt =60*8x = 480x


Distance covered in time of retardation,

v^2 = u^2 + at

=> u^2 = v^2 -at

0^2 =v^2 - 2bS3

S3=60^2/(2*60/x)

S3= 30x

so, total distance = 30x+480x+30x = 540x

Total time = x+8x+x =10x

so,
average velocity = total distance/ toatal time

540x/10x = 54km/h


Hope it helps