C2 - Foundations of Physics

Question 1

What’s the difference between a scalar and a vector quantity?

Answer 1

Scalar has magnitude but no directions.g. Distance, mass, time etc.

Vector has magnitude (size) and direction e.g. Weight, displacement etc.

Question 2

What are the seven (SI) base units?

Quantity/base unit/unit symbol

Answer 2

Length/metre/m

Mass/kilogram/kg

Time/seconds/s

Electric current/ampere/A

Temperature/kelvin/K

Amount of a substance/mole/mol

Luminous intensity/candela/cd (not needed)

Question 3

How are parallel and anti parallel vectors calculated?

Answer 3

Parallel vectors are added to find the resultant vector. E.g. 3N + 4N = 7N

Anti parallel vectors are made positive in one direction and negative in the other and then added together.

Question 4

How are perpendicular vectors calculated?

Answer 4

The resultant vectors are found by either calculation or a scale drawing/vector triangle.

Draw a line to represent the first vector
Draw a line to represent the second vector starting from the end of the first vector
To find the resultant vector, join the start to finish and use Pythagoras’ theorem (or count the distance if accurate).

Question 5

What is resolving a vector?

Answer 5

Reversing the procedure of adding perpendicular vectors to split a vector into two perpendicular components.
It can be done with a scale drawing or calculation.

Question 6

How do you resolve a vector?

Answer 6

To resolve a force F in directions x and y (x & y axis) , the two components of the force are:

Fx = FCosθ

Fy = FSinθ

where θ is the angle made with the x direction. These equations can be used with any vector in the place of x.

Question 7

A horizontal wind is blowing at 15ms-1 at an angle of 60° north of east.
Calculate the components of the wind velocity in the north and east directions:

Answer 7

1) Select the equations for resolving vectors:
(F=V symbol)
Vx = VCosθ
Vy = VSinθ

2) Substitute the values into the equations and calculate the components

Velocity east =
Vx = 15 (Cos 60°) = 7.5ms-1

Velocity north =
Vy = 15 (Sin 60°) = 13ms-1

You can quickly check your answer using Pythagoras theorem:
V2 = Vx2 + Vy2
= 7.5 2 + 13 2
= 56.25 + 169

V = 15ms-1

Question 8

How do you add non-perpendicular vectors?

Answer 8

1) Draw a scale diagram 
OR
2) Draw a triangle and use the sine and cosine rule
OR
3) Use Pythagoras theorum