Question

1. In a journey along a highway, a car cruises at30 ms for one hour and then takes 30 minutes
to travel 12 km in a heavier traffic condition. What is the average speed of the car for the
journey?
(a) 60 km h
(b) 66 km h
(c) 80 km h!
(d) 88 km h'​

Answer 1

Answer:

Explanation:

ANSWER:-

Given:-

• 1st case:-
• 30 m/s is the speed
• Time is 1 hour = 3600 seconds
• We need to find Distance

$\sf{Speed = \frac{Distance}{Time}}$

$\sf{30 = \frac{Distance}{3600}}\\\sf{Distance = 30 \times 3600} \\\sf{Distance = 108000 \ meters}$

• Second Case;-
• Time is 1800 seconds i.e 30 minutes
• Distance is 12 km = 12000 Meters.

$\sf{Average \ Speed = \frac{Total \ Distance}{Total \ Time}}$

$\sf{=\frac{108000+12000}{3600+1800}}\\\sf{= \frac{120000}{5400}}\\\sf{= 22.22 m/s$

= 79.99 Km/h (Converted)

So, c part is the correct Answer.

Things to Note:-

• Always convert the units to SI units
• If mentioned then do not convert
• In this I converted first to SI Units
• And then to km/h as it was mentioned
• SI Unit of Distance is metres
• SI unit of Speed is metre per second
• SI unit of time is seconds.