GENERAL PHYSICS
Uses of rules
Measuring the length of a piece of wire
Small length like thickness: measure several thicknesses and calculate average
Something curvy, lay a thread along the line and measure the thread
Uses of measuring cylinders
Measure volume of liquid
Measure volume of irregular shaped object by displacement
o Use a cylinder 4 times larger than object. Partially fill with water, enough to
cover object
o Immerse object in water. Increase in total volume = volume of the
object
1μm = 1 x 10m = 1 x 10-6 m (micrometer) 1nm = 1
x 10-9 m
Micrometer screw gauge: measure very small
distances
Turn barrel until jaws tighten on object. Friction
clutch ensures right pressure Length =
Mainscale + fractional scale reading
Timing device
Analogue clock: traditional clock, find time by looking at where the hands are
pointing on the scale
Digital clock: gives a direct reading of time in numerals
Light gate: measure the time taken for a rapidly moving object to move
between 2 points
Obtain an average value for a small distance and for a short interval of time by
measuring multiples
Speed: the distance travelled by an object per unit time
Velocity is a vector quantity because it has both magnitude and direction
Speed is a scalar quantity because it only has magnitude
Average speed = Total distance / Total time
Distance – time graph Speed – time graph
A: slopes up gently -> slow A: slope upwards -> accelerating
speed B: horizontal -> speed constant
B: steeper slope -> moving C: slope downward -> decelerating - negative
faster acceleration
C: horizontal -> stationary Distance = Area under speed-time graph
Steeper line -> higher speed Acceleration = Gradient
, GENERAL PHYSICS
Speed = Gradient
Straight line -> constant acceleration, linear
motion
Acceleration: the (positive) rate of change of an object’s velocity
Acceleration = Change in velocity / Time taken a = (v – u) / t
Acceleration of free fall: acceleration of an object falling freely under gravity
Constant near Earth g = 10 m/s2
1. Weight downwards, drag upwards -> accelerates
downwards
2. Eventually weight = drag -> resultant force = 0 ->
terminal velocity
3. Open parachute -> increase area and air resistance -
> bigger force upwards -> decelerates
Terminal velocity: greatest speed reached when moving through a fluid (constant)
Mass: the amount of matter an object Weight: the downward force of gravity
is made of that acts on an object because of its
mass
Not a force, measured in kg A gravitational force, measured in N
Scalar quantity Vector quantity
Constant on every planet Changed by magnitude of gravity
Compared using balance
Weight = mass x gravitational field strength W = mg
Density: the ratio of mass to volume for a substance (smaller density -> float)
Density = Mass / Volume ρ=m/V
Calculating + measuring density
For a regular shaped solid, find its volume by measurements and formula. Find
its mass using a balance then calculate the density
For a liquid place a measuring cylinder on a balance and set the balance to 0.
Pour liquid in a read the volume and mass then calculate the density
Force: action of one body on a second body that causes its velocity to change
Force = Mass x Acceleration F = ma
Makes object accelerate or change direction or shape, size
Uses of rules
Measuring the length of a piece of wire
Small length like thickness: measure several thicknesses and calculate average
Something curvy, lay a thread along the line and measure the thread
Uses of measuring cylinders
Measure volume of liquid
Measure volume of irregular shaped object by displacement
o Use a cylinder 4 times larger than object. Partially fill with water, enough to
cover object
o Immerse object in water. Increase in total volume = volume of the
object
1μm = 1 x 10m = 1 x 10-6 m (micrometer) 1nm = 1
x 10-9 m
Micrometer screw gauge: measure very small
distances
Turn barrel until jaws tighten on object. Friction
clutch ensures right pressure Length =
Mainscale + fractional scale reading
Timing device
Analogue clock: traditional clock, find time by looking at where the hands are
pointing on the scale
Digital clock: gives a direct reading of time in numerals
Light gate: measure the time taken for a rapidly moving object to move
between 2 points
Obtain an average value for a small distance and for a short interval of time by
measuring multiples
Speed: the distance travelled by an object per unit time
Velocity is a vector quantity because it has both magnitude and direction
Speed is a scalar quantity because it only has magnitude
Average speed = Total distance / Total time
Distance – time graph Speed – time graph
A: slopes up gently -> slow A: slope upwards -> accelerating
speed B: horizontal -> speed constant
B: steeper slope -> moving C: slope downward -> decelerating - negative
faster acceleration
C: horizontal -> stationary Distance = Area under speed-time graph
Steeper line -> higher speed Acceleration = Gradient
, GENERAL PHYSICS
Speed = Gradient
Straight line -> constant acceleration, linear
motion
Acceleration: the (positive) rate of change of an object’s velocity
Acceleration = Change in velocity / Time taken a = (v – u) / t
Acceleration of free fall: acceleration of an object falling freely under gravity
Constant near Earth g = 10 m/s2
1. Weight downwards, drag upwards -> accelerates
downwards
2. Eventually weight = drag -> resultant force = 0 ->
terminal velocity
3. Open parachute -> increase area and air resistance -
> bigger force upwards -> decelerates
Terminal velocity: greatest speed reached when moving through a fluid (constant)
Mass: the amount of matter an object Weight: the downward force of gravity
is made of that acts on an object because of its
mass
Not a force, measured in kg A gravitational force, measured in N
Scalar quantity Vector quantity
Constant on every planet Changed by magnitude of gravity
Compared using balance
Weight = mass x gravitational field strength W = mg
Density: the ratio of mass to volume for a substance (smaller density -> float)
Density = Mass / Volume ρ=m/V
Calculating + measuring density
For a regular shaped solid, find its volume by measurements and formula. Find
its mass using a balance then calculate the density
For a liquid place a measuring cylinder on a balance and set the balance to 0.
Pour liquid in a read the volume and mass then calculate the density
Force: action of one body on a second body that causes its velocity to change
Force = Mass x Acceleration F = ma
Makes object accelerate or change direction or shape, size
