# Physics Unit 1 Definitions

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Vector
A physical quantity that needs magnitude, direction and a unit.
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Scalar
A physical quantity that only needs magnitude and a unit.
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Displacement
The distance moved in a particular direction.
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Speed
The distance moved per second.
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Velocity
The displacement moved per second.
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Acceleration
The rate of change of velocity with time.
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Projectile
An object that is moving freely in the Earth's gravity, it moves with a horizontal component of velocity and a vertical component of velocity.
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Newton's First Law
If a body is at rest it will remain at rest, or if it is travelling with a uniform velocity (constant speed in a straight line) it will remain like this until a resultant force acts upon it.
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Newton's Second Law
The acceleration of an object is inversely proportional to its mass, directly proportional to the resultant force and it takes places in the direction that the force acts in.
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Newton's Third Law
If body A exerts a force on body B, body B exerts an equa
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## Other cards in this set

### Card 2

Scalar

#### Back

A physical quantity that only needs magnitude and a unit.

Displacement

Speed

Velocity