Question

In a car race, in a very busy road, a skilled driver has managed to drive his car with uniform velocity of
5 ms' for 10 minutes
Average speed of the car in first 2 minutes is
a) 2.5 ms
b) 7.5 ms
c) 10 ms
d) 5 ms​

Answer 1

Option D, 5m/s

The car drives for 10 minutes with uniform velocity of 5m/s.

Time t = 10 minutes = 10 × 60 seconds = 600 seconds.

Now, We can say,

Distance traveled = Speed * Time

Distance traveled in 10 minutes = 5 * 600 m = 3000m.

$\sf Average \: \: speed = \large \frac{ Distance }{Time }$

Since it's uniform motion, We can conclude Average velocity = Uniform velocity.

Now, Distance traveled in 2 minutes = 5 * 120 m = 600 m.

Average speed = 600 ÷ 120 = 5m/s.

One thing to note is

When we say a body is in uniform motion, It's instantaneous speed = average speed = uniform speed.

And Since, In the current question, The driver maintained a uniform speed till 10 minutes, Average speed = 5m/s ( = Uniform speed).

Taking any interval less than 10 minutes, gives you the same average speed.