Question

a car travels in a straight line with velocity of 80 km per hour for 2.5 hour and then velocity of minus 40 km per hour for 1.5 hour the average velocity of the car is

Answer 1

Average velocity = total displacement / total time taken
Here , total time = (2.5+1.5)hours= 4hours
Displacement in 2.5 hours= v×t= (80×2.5)= 200km
In 1.5 hours=v×t=-40×1.5=-60km
Total displacement=( 200-60)km=140 km
So, av. Velocity= 140/4= 35kmph

Answer 2

The average velocity of the car is 35 km/hr.

Step-by-step explanation:

We are given that a car travels in a straight line with a velocity of 80 km per hour for 2.5 hours and then the velocity of minus 40 km per hour for 1.5 hours.

Firstly, as we know that the formula for calculating average velocity is given by;

Average velocity  =  $\dfrac{\text{Total displacement}}{\text{Total time taken}}$

Here, the total time taken = 2.5 hours + 1.5 hours = 4 hours.

Now, we have to find the total displacement of the car.

Displacement in a straight line = Velocity $\times$ Time taken

So, $\text{Displacement}_1= 80 \times 2.5$

                             = 200 km

Similarly, $\text{Displacement}_2= (-40) \times 1.5$

                                       = -60 km

So, the total displacement of the car = $\text{Displacement}_1+ \text{Displacement}_2$

                                                               = 200 km + (-60) km

                                                               = 200 - 60 = 140 km

Now, Average velocity of the car  =  $\frac{\text{Total displacement of the car}}{\text{Total time taken by the car}}$

                                                        =  $\frac{140}{4}$  =  35 km/hr.

Hence, the average velocity of the car is 35 km/hr.