1.1 Basic Physics

Question 1

7 SI quantities

Answer 1

Mass, length, time, current, temperature, amount of substance, luminous intensity

Question 2

7 SI base uits

Answer 2

kg, m, s A, K, mol, cd

Question 3

How to find base units

Answer 3

1. Find equation
2. Find known units in equation
3. Solve equation

Question 4

An equation must be

Answer 4

homogeneous to be correct

Question 5

Homogeneous

Answer 5

Means the units are equal on both sides

Question 6

If 2 vectors are at 90 degrees you can add them using

Answer 6

sin(theta) = opposite/ hypotenuse

Question 7

A vector quanitity

Answer 7

has magnitude and direction

Question 8

A scalar quantity

Answer 8

has just magnitude

Question 9

Velocity=

Answer 9

displacement/ time

Question 10

Acceleration=

Answer 10

change in velocity/ time

Question 11

List of scalars

Answer 11

Density
Mass
Volume
Area
Distance
Length
Speed
Work
Energy
Power
Time
Resistance
Temperature
Voltage/ PD
Charge
Pressure

Question 12

List of vectors

Answer 12

Displacement
Velocity
Acceleration
Force
Momentum
Gravitational Field Strength

Question 13

To add more than one vector

Answer 13

Add them nose to tail

Question 14

To subtract vectors e.g. v2-v1

Answer 14

-v1 + v2

Question 15

Finding the component of a force is called

Answer 15

resolving; we resolve a force into its horizontal and vertical components

Question 16

Components of vectors using trig

Answer 16

Fh = Fcos(theta)
Fv = Fsin(theta)
F = Root{Fh^2 + Fv^2}

Question 17

Density (p)=

Answer 17

mass/ volume

Question 18

Density of air at 0 degrees

Answer 18

1.29 kgm^-3 or 0.00129 gcm^-3

Question 19

Density of water

Answer 19

1000 kgm^-3 or 1 gcm^-3

Question 20

Density of brick

Answer 20

2300 kgm^-3 or 2.3 gcm^-3

Question 21

Density of petrol

Answer 21

880 kgm^-3 or 0.88 gcm^-3

Question 22

Density of steel

Answer 22

7900 kgm^-3 or 7.9 gcm^-3

Question 23

Density of aluminium

Answer 23

2800 kgm^-3 or 2.8 gcm^-3

Question 24

Density of mercury

Answer 24

13600 kgm^-3 or 13.6 gcm^-3

Question 25

Density of gold

Answer 25

19300 kgm^-3 or 19.3 gcm^-3

Question 26

1 cm^3=

Answer 26

1 x 10^6 m^-3

Question 27

1000 kgm^3=

Answer 27

1gcm^-3

Question 28

Moment=

Answer 28

force x perpendicular distance

Question 29

The moment of a force is also called

Answer 29

its torque; the symbol t is also sometimes used

Question 30

The moment of a force is

Answer 30

the product if the force and the /perpendicular/ distance from the point to the line of action of the force

Question 31

Moments can be

Answer 31

clockwise or anticlockwise

Question 32

The principle of moments:

Answer 32

for a body to be in equilibrium under the action of a number of forces, the resultant moment about any point is zero- the sum of the clockwise moments is equal to the sum of the anticlockwise moments about the same point

Question 33

The centre of gravity is the point at which

Answer 33

we can consider all the object’s weight to act

Question 34

(In a uniform gravitational field) the C of G of a symmetric body of uniform density

Answer 34

will lie on any plane of symmetry

Question 35

For a standing object, to be more stable

Answer 35

it should have a lower C of G and a wider base

Question 36

A body is said to be in equilibrium if

Answer 36

it is moving and rotating at a constant rate

Question 37

In order to be in equilibrium

Answer 37

the resultant force on the object must be zero and the resultant moment about any point must be zero

Question 38

PRACTICAL: Measuring mass using the principle of moments

Answer 38

• Use known distances and one known mass
• Move the unknown mass until the ACM and CM are equal
• Calculate

Question 39

PRACTICAL: Absolute uncertainities

Answer 39

Often taken as +- 1 of the last digit of reading

Question 40

PRACTICAL: Measuring the density of solids

Answer 40

• Measure mass
• Measure volume
• Divide mass by volume
  Regular solids/ irregular solids (measure/ liquid displacement)