Question

A car starts from point P, travels 40 km due south and reaches Q, then takes a right
turn and travels another 30 km in a straight line to reach point R. The total time taken by
the car for this journey is 2 h 46 min and 40 s. Calculate the following:

a) Average speed of the car for this journey in m/s.

b) Average velocity of the car for this journey in m/s.​

Answer 1

a. average velocity = total distance traveled / total time taken

    total distance =  40 km + 30 km= 70 km

    total time =  2 hr 46 min 40 s = 10000 s

Now we know that the average velocity of a body is ratio of total displacement traveled to total time taken. In the attachment you can see and it is given that the cat turns right after 40km and the travels 30km. According to the attachment then the displacement of car will be, by Pythagorean theorem :  

h^2  = p^2 + b^2

h^2 = 40^2 + 30^2

h^2 = 1600 + 900

h^2 =  2500

h^2 = $\sqrt{2500}$ = 50

Therefore we get the displacement of car to be 50km = 50,000km

Now the average velocity of car will be :-

av = 50000m/ 10000 s

av= 5m/s

Therefore the average velocity of car is 5m/s.