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P4 ­ Explaining Motion
Speed, Distance, Velocity and Acceleration
Speed

Speed is the distance travelled in a certain time.

To find the speed of an object you need to know the distance it travels (meters) and the time it takes
(seconds). Use the formula:




This formula triangle shows that to…

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Velocity

Velocity is a useful measure of motion, as it describes both the speed and direction.

Instantaneous velocity is its speed and direction at a given moment in time.

Velocity Time Graphs

Important notes:

Gradient = acceleration
Flat sections represent moving in a straight line at constant speed
The steeper…

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The Three Types of Friction:

1. Friction between solid surfaces which are gripping

This is the friction that lets you walk around ­ the friction between your shoes and the ground allows
you to push against it and move forward. If there was no friction then you would slip and…

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So if the arrows come in opposite pairs, and they are all the same size, then the forces are
balanced

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Resultant Force

In many situations, the force acting on an object are not all the same ­ meaning that they are
unbalanced.

The resultant force is the overall force acting on an object ­ the force you get when you take into
account all the individual forces and their directions.…

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When a resultant force acts on an object, it causes a change in momentum in the direction of the
force. The change of momentum it causes is proportional to the size of the force and the time it acts
for. So, the bigger the force and the longer it acts…

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Increase in Kinetic energy = Work done

So if work is done on an object, then energy is transferred to that object which will make it start
moving or to move faster. In physics, energy is always conserved. This means that you can't create or
destroy energy ­ it just…

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Ashvarya

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Really helpful, thanks!

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