1.1 Basic Physics Flashcards
Symbol for mass
m
Symbol for length
l
Symbol for time
t
Symbol for electric current
I
Symbol for temperature
T
Symbol for amount of substance
n
Symbol for luminous intensity
L
Unit of mass
kilogram (kg)
Unit of length
metre (m)
Unit of time
second (s)
Unit of electric current
ampere (A)
Unit of temperature
kelvin (K)
Unit of amount of a substance
mole (mol)
Unit of luminous intensity
candela (cd)
Equation for area
area=length*breadth
Unit of area
m^2
Equation for change of speed or velocity
change of speed=final velocity-initial velocity
Unit of change of speed/velocity
ms^-1
Equation for acceleration
acceleration=change of velocity/time a=Δv
Symbol for acceleration
a
Unit of acceleration
ms^-2
symbol for change of speed/velocity
Δv
Equation for Force
Force=mass*acceleration F=ma
Symbol for force
F
Unit of force
Newtons (N) (kgms^-2)
Equation for work
Work=Force*distance
Unit of work
Joules (J) (kgm^2s^-2)
Equation for Power
Power=work/time
Unit of power
Watt (W) (kgm^2s^-3)
What are the rules for homogentity?
- Two quantities can only be added together if the have the same units, and the answer has the same units.
- An equation is homogeneous only if the units of the two sides are the same.
What is a vector quantity?
A vector quantity has magnitude and direction, eg Force
What is a scalar quantity?
A scalar quantity just has magnitude eg mass
What is resultant force?
The combined effect of two or more forces is called the resultant force (Fres) [res is subscript]
How do you calculate Resultant Force?
Use the cosine rule of Pythagoras’ theorum
Symbol for Resultant Force
Fres [res is subscript] or ΣF
What is displacement?
The distance and direction from A to B, in a straight line/ eg point A is 9cm W of point B
Equation for velocity
velocity=displacement/time
Unit for velocity
metres per second in a stated direction (ms^-1 at compass point)
Equation for acceleration
acceleration=change of velocity/time a=Δv/Δt
How do you add and subtract vectors?
Use nose-to-tail method
What is “resolving” a force?
Calculating the horizontal and vertical components
Equation for Density
Density=mass/volume ρ=m/V
Symbol for density
ρ
Unit of Density
kgm^-3 or gcm^-3
Approximate density of air
1.29ρ/kgm^-3 0.00129ρ/gcm^-3
Approximate density of water
1000ρ/kgm^-3 1.00ρ/gcm^-3
Approximate density of brick
2300ρ/kgm^-3 2.30ρ/gcm^-3
Approximate density of petrol
880ρ/kgm^-3 0.88ρ/gcm^-3
Approximate density of steel
7900ρ/kgm^-3 7.90ρ/gcm^-3
Approximate density of aluminium
2800ρ/kgm^-3 2.80ρ/gcm^-3
Approximate density of mercury
13600ρ/kgm^-3 13.6ρ/gcm^-3
Approximate density of gold
19300ρ/kgm^-3 19.3ρ/gcm^-3
What would the width of 1 tonne of interstellar space be?
10^6km
What would the width of 1 tonne of red giant star be?
100m
What would the width of 1 tonne of the sun be?
0.89m
What would the width of 1 tonne of a white dwarf be?
8.9mm
What would the width of 1 tonne of a neutron star be?
15µm (micro metres)
How do you convert cm^3 to m^3?
1 cm^3 = 1*10^6 m^3
How do you convert density from kg-g?
1000kgm^-3 = 1.00gcm^-3
Define torque/ the moment of a force
The product of a force multiplied by the perpendicular distance from the line of action to the pivot.
Unit of moment/Torque
Newtons per metre (Nm)
Symbol for torque/moment of a force
t
What is the principal of moments?
For a body to be in equilibrium under the action of a number of forces, the resultant moment about any point is zero.
Define equilibrium
A body is in equilibrium if it is moving and rotating at a constant rate. In order for this to happen:
- The resultant force on the object must be zero.
- The resultant moment around any point must be zero.
How would you measure the density of a regular solid?
Calculate the volume using
Volume of a cuboid= lbh
Volume of a cylinder = Al = π r^2 l = (π r^2 l)/4
How would you measure the density of a irregular solid?
Submerge the solid in a measuring cylinder of water and measure the displacement of the water.
