Foundation of Physics

Question 1

What is the SI base unit for : length?
mass?
time?

Answer 1

Length - Meters (m)
Mass - Kilogram (kg)
Time - Seconds (s)

Question 2

What is the SI base unit for:
Current?
Temperature?
Amount of x?

Answer 2

Current - Ampere (A)
Temperature - Kelvin (K)
Amount of Substance - Mole (mol)

Question 3

Are unit Symbols Capital or Lowercase?

Answer 3

Units are written in lowercase unless they are named after a person, in which case the name still begins with a lowercase
e.g. ampere - A

Question 4

Derived SI units
- Some quantity are used so much much they have their own units.
What is the unit for Force in terms of SI units?
-Pressure?
-Resistance?
-Charge?
-Power?
-Potential Difference?

Answer 4

Force - N - kgms^-2

Pressure - Pa - Nm^-2 - kgm^-1s^-2

Resistance - Ohms - VA^-1 - Jc^-1A^-1 - Js^-1

Charge - C - As

Power - W - Js^-1

Potential difference - V - JC^-1

Question 5

Can Scalars be added/subtracted?
What is the contition?

Answer 5

Yes they can e.g 50g - 20g = 30g

However they must be in the SAME units

Question 6

Can you multiply/divide scalars?

Answer 6

Yes but they must be dervived
e.g Density = Mass/Volume = kgm^-3

Question 7

How do you combine:
Two parallel vectors?
Two anti parallel vectors? (opposite directions but parallel)

Answer 7

If vectors are parallel you can add them together to find the resultant vector

If vectors are anti-parallel, make one positive and one negative and sum them to find the resultant vector.

Question 8

How do you calculate the resultant magnitude and direction given 2 perpendicular vectors?

Answer 8

1) Scale drawing - Draw tip to Tail
2) Pythagoras

Question 9

How do you resolve a vector into its horizontal and vertical componants?

Answer 9

Resolve F into Fx and Fy
Fx = F cos theta
Fy = F Sin theta

Question 10

How do you add non perpendicular vectors?

Answer 10

1) Draw out tip to tail
2) Use cosine rule to determine resultant force (a^2=b^2+c^2-2bccosA) then use sine rule to determine resultant angle (SinA/a = SinB/b –> Sin^-1(axSinB/b)
3) Find horizontal and vertical componants, sum and find resultant.

Question 11

How do you subtract Two vectors?

Answer 11

E.g —> = x upwards = y
To subtract x from y, reverse the direction of y and then find the resultant.

Question 12

What is the difference between Scalar and vector quantitys.

Answer 12

A vector has direction whereas a Scalar does not.

Question 13

What does percentage uncertainty tell us?

How is absolute uncertainty represented?

Answer 13

% uncertainty tells us how far out (as a %) we should expect to be our final value compared with the therotically correct value, due to our equipment & method.

+/- = Absolute uncertaity
= sine of range of values in which the true value probably lies

Question 14

How do you calculate percentage Uncertainty?

Answer 14

% uncertainty =
(+/- / value) x 100

Question 15

Rules of % uncertainty in calculations
What is the percentage uncertainty when:
1) a = bc
2) a = b + c
3) a = b / c
4) a = b^2

Answer 15

1) (% uncertaity in b) + (% uncertainty in c)
2) biggest uncertaity of the two
3) ( % unc in b) + (% unc in c)
4) 2(% unc in b)
5) a=b^3 = 3(% unc in b)

Question 16

What is the line of worst fit?

(worst line of best fit)

Answer 16

The line of worst fit is a line with the greatest or least slope, away from the line of best fit that still goes through all or nearly all error bars

Question 17

How do you calculate % uncertainty in gradient
and
Y intercept using LOBF and LOWF?

Answer 17

% uncertainty in gradient =
differnece between gradients/LOBF gradient.

% unc in Y-intercept = Intercept of worst - intercept of best / intercept of best x 100
= (Cw - Cb / Cb) x100

Question 17

What is the Symbol/Power For:
Kilo?
Deci?
Milli?
Centi?

Answer 17

Kilo - K - 10^3
Deci - d - 10^-1
Centi - c - 10^-2
Milli - m - 10^-3

Question 18

What is the symbol/power for:
Micro?
Nano?
Pico?

Answer 18

Micro - |u - 10^-6
Nano - n - 10^-9
Pico - p - 10^-12

Question 19

What is the symbol/power for:
Mega?
Giga?
Tera?
Peta?

Answer 19

Mega - M - 10^6
Giga - G - 10^9
Tera - T - 10^12
Peta - P - 10^15

Question 20

cm^2 —> m^2 ?

Answer 20

x 10^-4 not x 10^-2

Question 21

What is a scalar quantity and examples?

Answer 21

A physical quantity with MAGNITUDE only.
Examples :
speed
distance
charge
time
amount of substance
mass
temperature
resistance
potential difference

Question 22

What is a vector quantity and examples?

Answer 22

A physical quantity with magnitude and direction
Examples:
acceleration
current
electric field strength
weight
momentum
force
velocity
displacement
magnetic flux density

Question 23

What are the rules for adding vectors?

Answer 23

1) ALWAYS add vectors by drawing them out joined tip - to - tail
2) The resultant vector is given by the vector joining the start point to the end point

Question 24

How do you resolve vectors into two perpendicular components?

Answer 24

• Each component vector will be smaller than the inital vector
• The magnitude of one of the componets will ALWAYS be equal to the inital vector x sin of the angle given
• The magnitude of one of the componets will ALWAYS be equal to the inital vector x cos of the angle given.

Question 25

Rules for significant figures when:
- + or -
- x or divide

Answer 25

+ or -
give answer to same sig fig as least precise number in the calculation (nearest whole number)

x or divide
use same number of sig fig as the value with the least sig fig in calculation

Question 26

Length, area, volume
1mm = ?m
1mm^2 = ?m^2
1mm^3 = ?m^3

Answer 26

1mm = 1x10^-3m
1mm^2 = (1x10^-3)^2 = 1x10^-6
1mm^3 = (1x10^-3)^3 = 1x10^-9