# Explaining Motion

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Speed  can be worked out if you know:

• The distance travelled.
• The time taken to travel that distance.
• Speed (m/s) = Distance (M)/ Time (S)
• Their average speed can be calculated from the total distance and total time taken.
• Their speed at any one time is called the instantaneous speed.
• If we indicate the direction something is traveling in we can use positive distance and negative distance.
• Velocity and speed both tell us how fast something is moving, but velocity also takes account of direction.
• If we say that an object is moving away from the staring point, we say that it has a positive velocity.
• Then it has negative velocity when it travels back down.
• Forces arise when objects interact with each other.
• The size of the force is measured in Newtons.
• If you apply force on an object, the object with apply a force back on you.
• This is called the Reaction Force
• Forces always act in pairs like this.
• Friction is a force that opposes motion.
• Lubricants such as oil are often used to reduce friction.
• Forces can…