Speed and Velocity

Speed is the distance traveled in a given amount of time.

Speed= distance time The units for speed: meters/second (m/sec) kilometers/hour (km/hr)

Speed and Direction: VelocityIn describing the motion of an object, we do not just describe how fast the object moves. We also consider the direction to where it is going. Speed with direction is referred to as velocity.

The sample weather bulletin below will show you the importance of knowing not just the speed of the storm but also its direction.

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Whenever there is a storm coming, we are notified of its impending danger in terms of its speed and direction. Aside from this, we are also informed about its strength.

Do you know that as the storm moves, its winds move in circles? The circular speed of the winds of the storm determines its strength. Different storm signals are given in places depending on the circular speed of the winds of the storm and the distance from the center.

Study again the weather bulletin above. Which is the speed for the circular motion of the typhoon winds?

Which is the speed for the motion of the storm as a whole along the path?

How important are speed and direction in determining the weather forecast for the next hours?

Constant vs Instantaneous SpeedIf you solved for the distance travelled by each participant over the time he took to cover such distance, then you have computed for his average speed.

But why average speed and not just speed?

It is considered average speed because it represents the speed of the participant throughout his travel. During his travel, there were instants that his speed would vary.

His speed at an instant is called instantaneous speed.

Similarly, the velocity of a moving body at an instant is called instantaneous velocity.

The instantaneous speed may be equal, greater than, or less than the average speed.

When an object’s instantaneous speed values are always the same, then it means that the object is moving with constant speed. We refer to this as constant motion.

Where you will be and what time you will reach your destination is easily predicted when you move at constant speed or velocity.

(Explain the statement.)