Page 169 - Science Class 07

18000
Speed in metre/minute = Speedometer displays the speed of the moving
60
= 300 metre/minute vehicles. It is marked from 0 to 180 or from 0 to
260 mark. It also consists of a needle that
Distance = Speed × Time
moves over the marked digits. If the needle
= 300 m/minute × 20 minute points to 50, it means the vehicle is moving

= 6000 m with the speed of 50 km/h. Speedometer works
on the principle of the distance covered by the
= 6 km
type of the vehicle in one rota on.
Finding Time
Example : A motorcycle is moving with a speed
to 60 km/h. How much me it will take to cover

540 km?
Speed = 60 km/h

Distance = 540 km
Distance 540
Time = = = 9 km
Speed 60

DEVICES USED TO MEASURE DISTANCE AND
SPEED OF MOVING OBJECTS

Fast moving vehicles have odometer and Speedometer
speedometer a ached to them.
Suppose, the radius of the tyre of a vehicle is
Odometer displays the distance covered by the
63 cm. Let’s find the distance covered by it in
vehicles in kilometres. It has generally six one rota on. The distance covered by the tyre
columns and every column has the digits from
in one rota on will be equal to its perimeter.
0 to 9. These digits move upwardly when the
So, distance = 2 pr
vehicles move. It can represent distance upto 9
lakh 99 thousand 9 hundred and 99 km. = 2 × 3.14 × 63
= 396 cm
or = 3.96 metre

It means the vehicle will move 3.96 metre
further its tyres make one rota on.
Similarly, we can find out the number of
rota on made by the vehicle if it covers a
distance of 1000 metre.

Number of rota on if the vehicle moves
Odometer 1000
1000 metre = = 252.53
v The odometer of a motor car displays the 3.96
following digits. What will be the digits if Now, we can say that if the tyres rotates around
the car moves 6575 km more? 252 mes, the vehicle will cover a distance of

4 5 6 0 7 0 1000 metres or 1 kilometer.

Science-7 169