# Physics AS notes OCR

- Created by: JPopat
- Created on: 10-01-13 17:45

First 347 words of the document:

Physics AS Level Summary

*Points to help remember definitions etc.

SCALARS AND VECTORS:

A SCALAR quantity has magnitude only and is completely described by a number and

appropriate units. *'scale' is a measure so magnitude only.

A VECTOR quantity is completely described only if both its magnitude and direction are

stated. *mathematical vectors in translation tell you where to go (direction) and by how

many units (magnitude)

To determine whether a quantity is scalar or vector, think about if you are given a direction in

your answer. *If it can be a negative value it is usually a vector quantity.

VECTOR TRIANGLES:

Join the forces head to tail, join the ends to find the resultant;

Resultant

If it is a right angled triangle, use Phythagoras' Theorem (a2+b2=c2)

If not, use Trigonometry (SOHCAHTOA)

You can also use SCALE DRAWING to find the resultant.

1. State the scale e.g. 1N = 1cm

2. Draw accurately to scale (both length and angle)

3. Use the diagram to measure the size and direction of the resultant.

NOTE: Force is a vector quantity so remember to measure both magnitude (force) and

direction (angle)

RESOLVING VECTORS:

If you are given one force and an angle, use Trigonometry (SOHCAHTOA)

NOTE: You can use this to find horizontal and vertical components.

DISPLACEMENT, SPEED AND VELOCITY:

DISPLACEMENT is the straight line distance travelled in a stated direction.

NOTE: displacement is a vector quantity whereas distance is scalar.

INSTANTANEOUS SPEED is the speed at a given instant of time.

AVERAGE SPEED = DISTANCE / TIME *Speed is scalar so use distance (because it is also

scalar)

VELOCITY = DISPLACEMENT / TIME *Velocity is a vector so displacement is used.

ACCELERATION = CHANGE IN VELOCITY / TIME *this is the gradient on a velocity/time graph.

Conventionally, upwards or forwards is positive and so downwards or backwards is

negative. For example, acceleration due to gravity would be, g = -9.81ms-2

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