Question

Q-1)A motorcyclist drives from place AtoB with a uniform speed of 30 km/h and returns from place BtoA with a uniform speed of 20km/h find his average speed.

Q-2) An aircraft travelling at 600km/h accelerates steadily at 10km/h per second .Taking the speed of sound as 1100km/h at the aircraft altitude ,how long with it take to reach the "sound barrier"?

Q-3)What is the change in momentum of a car weighing 1500kg when it's speed increases from 36km/h to 72km/h uniformly.

(PLEASE ANS CORRECTLY )*

*Don't give meaningless ans otherwise it's delete ❕❕

Answer 1

the answer q.1 we need to get average 
the answer 24 km per hour
q.2 is in the photo
q.3 starting momentum: 1500*36 final momentum: 1500*72 
That gives you momentum in kg-km/hr 
you probably want it in kg-m/s, so you need to convert km/hr to m/s.

Answer 2

Q1:
Distance from A to B:   s km  (say)
From A to B :   speed u = 30 kmph    Time taken:  s/30 hrs
         B to A :   speed v = 20 kmph                         s/20 hrs

Total time taken for two legs:  s* [1/30 +1/20] = s/12  hrs
Average speed = distance/duration = 2s/(s/12) = 24 kmph

Q2:
u = aircraft speed = 600 kmph = 600*5/18 = 3,000/18 m/s
a = acceleration = 10 kmph / sec = 10 * 5/18  m/s² = 50/18 m/s²
speed to reach = speed of sound = v = 1100 km/h
   = 1,100*5/18 = 5,500/18 m/s

   equation of motion = v = u + a t
   t = (v-u)/a = (5,500 - 3,000)/50  sec
     = 50 sec

Q3:

Mass of car = m = 1, 500 kg
initial speed = u = 36 km/h = 36*5/18 = 10 m/s
Final speed = v = 72 km/h = 72 * 5/18 = 20 m/s
Momentum = p = mass * speed 
Change in momentum = Δp = m (v - u)
    = 1, 500 * ( 20 - 10) = 15, 000 kg-m/s

Change in momentum depends on initial and final conditions. Car is traveling in a straight line - it is assumed.