Question

A car covers a distance of $160Km$ between two cities in $4Hr$. What is the average speed of the car?

Answer 1

Hint: We need to find the average speed. Here nothing is mentioned about the change in the direction or speed of the car in moving from one place to the other. Hence we are going to assume that average speed is nothing but the speed of the car.

Formula used:
$\text{Speed = }\dfrac{\text{Distance}}{\text{Time}}$

Complete answer:
Here, we need to find the speed of the car as in this case, average speed is nothing but the speed of the car.
Here, the distance travelled by the car from one city to the other = $160Km$
Also, the time taken by the car to reach from one city to the other = $4Hr$
We know that the speed of the body is nothing but the distance travelled per unit time interval.
This can be written in the equation as:
$\text{Speed = }\dfrac{\text{Distance}}{\text{Time}}$ ------(i)
Here,
$\text{Speed = }\dfrac{160Km}{4Hr}$
$\text{Speed = }40Km/hr$ -----(ii)
Hence, the average speed of the car moving from one city to the other is $40Km/hr$.

Additional information:
Speed is defined as the distance travelled by a body per unit time. If a body has moved from its place, the speed can never be zero. On the other hand, velocity is defined as the displacement of the body per unit time. The displacement of a body may or may not be zero. If the body reaches the same point from where it had started, then the velocity of the body becomes zero. But in the same case the speed will not be zero.

Note: Do not get confused by the ‘average speed’ mentioned. Here, the term average speed implies nothing but the term speed itself. The average speed and the speed of an object is different only if the object covers different distances at different speeds. In that case we need to find out the average of all the speeds.