6th Class Science Related to Competitive Exam Distance and Speed

     Distance and Speed

The length between two points or two towns is known as the distance between them the unit of distance is metre, kilometre etc. Long distance is measured in kilometre and short distance is measured in metre, centimetre and millimetre.

Look at the following table:

Speed is defined as the distance travelled in per unit time. If a car travels at a distance of 40 km in one hour then the speed of the car =

\[\frac{Travelled\,dis\tan ce}{Time\,taken}=\frac{40}{1}=40\] Km in one hour, which is written as 40km/hour

Speed can also be denoted by some other unit like metre per second, kilometre per second, kilometre per minute etc. Speed is also termed as velocity. A speed measuring instrument which is widely used is in vehicles is called speedometer.

Look at the following picture of speedometer and odometre:

Speedometer is a measuring device which shows the running speed of the vehicle. Odometer is also a measuring device but it shows the distance travelled by the vehicle.

A sensor on the wheel of the vehicle senses the rotation of the wheel and it sends the sensed signal to the speedometer. Speedometer receives the signal and its digital or analog panel show the travelled distance as per the time divisions of the speedometer.

Uniform and non-uniform Speed

When a car runs on a straight path with constant speed then the car is called in uniform speed. If the speed of the car varies with respect to the variation in time then the car is called in non-uniform speed.

Look at the following time distance graph for uniform speed:

In the graph above, travelled distance in 1 minute is 1 km, in 2 minutes, travelled distance is 2 km. Therefore, speed does not change or remains constant at 1 km per minute (1 km/m) which is called uniform speed and graph of uniform speed is always a straight line.

Look at the following time distance graph for non-uniform speed:

In the time and distance graph above, distance travelled in 1 minute and distance travelled in next 1 minute are not equal. Therefore, this is called non-uniform speed.

       Consider the following statements:

Statement 1: A car whose speed is constant is called in uniform speed.

Statement 2: A car whose speed is not constant is called in uniform speed.

Which one of the following is correct about the above statements?

(a) Statement 1 is true and 2 is false

(b) Statement 1 is false and 2 is true

(c) Both statements are false

(d) Both statements are true

(e) None of these

Answer: (a)

Explanation 

A car whose speed is constant is called in uniform speed. Therefore, option (A) is correct and rest of the options is incorrect.

       What type of speed does a curved on distance time graph line represent?

(a) Uniform speed

(b) Non uniform speed

(c) Rectilinear

(d) All of these

(e) None of these

Answer: (b)

Explanation 

A curve line on a distance- time graph represents non-uniform speed.

Therefore, option (B) is correct and rest of the options is incorrect.