Question

A car moving at a constant speed of 36 kmph
moves north wards for 20 minutes then due
to west with the same speed
minutes.
what is the average velocity of the car during
this run in kmph
1) 27.5 2) 40.5 3)20.8 4) 32.7
​

Answer 1

Answer:

Explanation:

=> Here, a car moving at a constant speed of 36 kmph moves north wards for 20 minutes.  

Speed = 36 km / h

Time, t1  = 20 mins = 20/60 hours = 1/3 hours (because 1 min = 1/60 hours)

Distance travelled towards north, S1 = Speed * time (t1)

= 36 km/h * 1/3 h

= 12 km

=> Car move towards west with the same speed for 8 * 1/3 minutes. Thus,

Speed = 36 km/h

Time, t2 = 8 * 1/3 = 25 / 3 minutes = 25 / 3 * 1/60 h = 25 / 180 h= 5/36 h

Distance travelled towards west, S2 = Speed (s) * time (t2)

= 36 * 5 / 36

= 5 km

Now, the average velocity of the car during this run:

V_avg = ΔS / Δt

=  √ S1² + S2² / t1 + t2

$=\frac{\sqrt{(12)^2+(5)^2} } {\frac{1}{3} + \frac{5}{36}}$

$= \frac{\sqrt{144 + 25}}{\frac{12 + 5}{ 36}}$

= 13 * 36 / 17

= 27.5 km/h

Thus,  the average velocity of the car during  this run is 27.5 km/h.