## 2009-02-09

### Distance, Displacement, Velocity, Speed and Acceleration

Distance and Displacement

Distance is the total path length traveled from one location to another. It is a scalar quantity.

Displacement is the distance between two locations measured along the shortest path connecting them, in specified location. It is a vector quantity. The SI unit of distance and displacement is metre (m).

Speed and Velocity

Speed is the distance traveled per unit time or the rate of change of distance.

Speed = total distance traveled / time taken

Velocity is the speed in a given direction or the rate of change of displacement.

Average velocity = displacement/ time taken

Acceleration and Deceleration

Acceleration is the rate of change of velocity.

Acceleration = change of velocity / time taken

Change of velocity = final velocity (v) – initial velocity (u)

Acceleration = (final velocity – initial velocity) / time taken
= (v – u) / t

Things to remember:

1. Constant velocity means the object is not accelerating. Acceleration is zero.
2. Constant acceleration means the object is increasing its velocity.

#### 5 comments: BJ said...

can you give more explanatory definations

O Dean said...

Hi BJ,

Distance is a scalar quantity, it does not have direction but only value (magnitude). So let say you travel along a triangle the sum of the length of the two sides comprises the distance(because you actually walk along and pass trough the path)

Whereas, a Displacement is the shortest distance between two points,and it has a magnitude and direction. say you want to travel from point A to B in a triangle, but you can not be bothered to walk through the two sides..so the shortest distance would be to walk through the hypotenuse with a specific angle towards say point B.

Speed is the distance traveled per time taken (note: distance, hence, it is a scalar quantity)

Velocity on the other hand is displacement traveled per unit time (note: displacement, hence, it is a vector quantity)

Acceleration is the rate of change of velocity. It is therefore a vector quantity. In layman's term, when you observe that there's a change in velocity... aka you are getting faster you accelerates... on the other hand, if your velocity is decreasing, you decelerate.

Remember: Accelerate - getting faster. Decelerate - getting slower Anonymous said...

Thankyou.

shadab karnachi said...

thanks you made my 9th physics easier

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Macky
www.imarksweb.org