p: unit 2, topic 1 - linear motion and force

what is a physical quantity and give an example

PE

• property that can be measured

• e.g. length (m), mass (kg)

speed

FRSS

• formula: speed = distance/time

• rate: the rate at which an object moves

• scalar quantity

• SI unit: ms^-1

what are scalar quantities and give examples

MDE

• magnitude: the types of physical quantities that are described only by a magnitude

• direction: no direction

• e.g. time (s), speed (ms^-1)

what is a vector quantity and give an example

DP AE

• direction: physical quantity that has both magnitude and direction

• positive: can be positive or negative

• algebraically: can be depicted algebraically or graphically

• e.g. displacement, velocity

how to notate vectors

BAT

• bold letters

• arrow notation

• tilde: using a tilde (same thing above the fancy spanish N)

distance

ESS

• entire: the entire length travelled by an object

• scalar quantity

• SI unit: metres (m)

displacement

OVS

• overall: the overall change in position of an object

• vector quantity

• SI unit: metres (m)

velocity

FRVS

• formula: velocity = displacement/time

• rate: the rate of change of an object’s displacement

• vector quantity

• SI unit: ms^-1

conversion from km hr^-1 to ms^-1

acceleration

VV PSQF

• velocity: rate of change of velocity

• vector quantity

• pos: can be pos or neg

• SI unit: ms^-2

• quickly: refers to how quickly an object is speeding up or slowing down

• formula: acceleration = change in velocity/time

average velocity

OF

• overall: describes the overall rate of motion across a journey

• formula: total displacement/total time

instantaneous velocity

SSV

• specific: describes how fast an object is moving at a specific moment

• slope: represented by the slope of a position-time graph

  • velocity: velocity can be read directly off the graph for a given point in time

what are the 3 main graphs of motion that help us to depict displacement, velocity and acceleration of an object

DVA

1. displacement-time

2. velocity-time

3. acceleration-time

displacement-time graphs

TDD VNY

• time is the independent variable (x-axis)

• displacement is the dependent variable (y-axis)

  • directly: can be read directly off graph

• velocity: given by gradient

  • negative gradient means change in direction

• y-intercept shows the position from which the object begins

error bars

UPF

• uncertainty: graphically represent the uncertainty in the data

• precise: help convey how precise/reliable the data is

• fit: can be used to insert maximum and minimum lines of best fit

line of best fit

TSV

• trendline: aka trendline

• straight line drawn through a scatter plot of data points that best represents the relationship between the variables

• visualise: used to visualise the trend/correlation in the data and make predictions about one variable based on the value of another

what are the 3 lines of best fit

AMM

1. average

2. minimum

3. maximum

velocity-time graphs

DTV AID

• displacement: given by area under the curve

  • total: displacements above the x-axis are added, and areas under the x-axis are subtracted to give the total displacement

• velocity: read directly from graph

• acceleration: given by gradient slope

• instantaneous velocity can also be determined for a particular point in time

• displacement: can be constructed from the gradient of the displacement-time graph

acceleration-time graphs

VA

• velocity: given by area under the graph

• acceleration: can be read directly off the graph

SUVAT

• the variables arising in a situation involving constant acceleration

S: displacement (m)

U: initial velocity (ms^-1)

V: final velocity (ms_-1)

A: acceleration (ms^-2)

T: time (s)

what are the three main equations of motion?

1. final velocity

2. displacement

3. final velocity squared

definition of gravity

the force that attracts objects with mass toward each other, particularly pulling them toward Earth’s centre

acceleration due to gravity

CG VMP

• constant: objects fall at a constant (uniform) rate close to the Earth’s surface

  • gravity: this constant is gravity, g, and its value is 9.8ms^-2 close to the Earth’s surface

  • velocity: as an object falls to the ground, its velocity increases by 9.8ms^-1

  • mass: applies to all objects, regardless of mass

• planet: varies based on planet