# Kinematics

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• Created by: Jane
• Created on: 07-04-13 20:50

First 230 words of the document:

Kinematics:
Displacement is the shortest distance from an initial position to a final position, it is a vector a
quantity and so has both magnitude and direction.
Instantaneous speed is the speed of a body at a particular instant in time.
Average speed is a measure of the distance travelled by a body in a given period of time; it is
sometimes referred to as the distance per time ratio. It is a scalar quantity.
Velocity is speed in a given direction; it is defined as the ratio of change in displacement and time
taken. It is a vector quantity.
Acceleration is defined at the ratio of change in velocity and time taken. It is a vector quantity and so
has a direction associated with it. When the velocity of an object increases the change in speed is
positive and the acceleration is positive whereas when the velocity decreases the change in speed is
negative and the acceleration is negative.
Distance-time graphs:
The gradient of the line at any point gives the speed of an
object
Displacement-time graphs:
This shows the displacement of a ball being thrown in the
air.
Displacement (unlike distance) can increase or decrease.
The gradient of the line gives the magnitude of the
velocity.

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Velocity-time graphs:
The area between the line and the time-axis of a
velocity-time graph represents distance travelled by
an object.
The gradient of a velocity-time graph represents
acceleration.
Velocity (unlike speed) can be both positive and