Motion, forces and energy

1. Describe the use of rulers and measuring cylinders to find a length or a volume

a ruler is used to measure length (unit: m)

to find the volume of a regular solid, use a ruler to measure the dimensions, than use an appropriate equation to calculate volume

fill a measuring cylinder with water and read the initial volume, submerge the object measure final volume, change in volume = volume of object

1. Describe how to measure a variety of time intervals using clocks and digital timers

1. Determine an average value for a small distance and for a short interval of time by measuring multiples (including the period of oscillation of a pendulum)

vector quantity

a vector quantity has magnitude and direction

force, weight, velocity, acceleration, momentum, electric field strength and gravitational field strength

scalar quantity

a scalar quantity has magnitude (size) only

distance, speed, time, mass, energy and temperature

speed

distance per unit time

velocity

displacement per unit time

Calculate speed from the gradient of a straight- line section of a distance–time graph

gradient = y2-y1/x2-x1

Calculate distance travelled in a speed-time graph

area under the graph

acceleration

change in velocity per unit time

a = ∆v/∆t

Calculate acceleration from the gradient of a speed–time graph

deceleration

negative acceleration

Describe the motion of objects falling in a uniform gravitational field with air/ liquid resistance

drag forces oppose the motion of objects and slow down objects

Describe the motion of objects falling in a uniform gravitational field without air/ liquid resistance

the acceleration of all objects falling without air/liquid resistance is constant, forces of gravity causes objects to accelerate downwards

g= 9.8m/s^2they

terminal velocity

as an object starts falling it will accelerate due to gravity, air resistance also increases so resultant force decreases and acceleration of object decreases. as object continues air resistance becomes equal to wieght, now continues with constant speed called terminal velocity

mass

the amount of matter in an object

weight

gravitational force acting on an object

W= m(g)

denisty

mass per unit volume

ρ = m/V

Determine whether an object floats based on density data

denser sinks to the bottom

Determine whether one liquid will float on another liquid based on density data given that the liquids do not mix

less dense floats on more dense

effects of forces

forces may produce changes in the size and shape of an object

newtons first law

an object either remains at rest or continues in a straight line at constant speed unless acted on by a resultant force

resultant force

change in momentum per unit time

resultant force may change

the velocity of an object by changing its direction of motion or its speed

friction

a force that opposes motion and produces heat

friciton acts on..

an object moving through a liquid and a gas ( air resistance )

spring constant

force per unit extension

k = F/x

limit of proportionality

moment of a force

the turning of a force

force × perpendicular distance from the pivot

principle of moments

at equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments

object in equilibrium

no resultant force and no resultant moment

centre of gravity

a single point through which the force of an objects weight acts

Describe an experiment to determine the position of the centre of gravity of an irregularly shaped plane lamina

1. suspend the object and a plumb line from the same point

2. trace the thread of the plumb line with a pencil

3. repeat using different points

4. the centre of mass is where all the lines cross

momentum

the product of mass and velocity

p=mv

impulse

the product of force and time or change in momentum

F∆t = ∆(mv)

principle of the conservation of momentum

change in momentum

∆p= m(v-u)

energy

ability or capacity to do work

energy can be stored as..

kinetic, gravitational potential, chemical, elasatic, thermal, nuclear and electrostatic

Describe how energy is transferred between stores during events and processes

as a ball falls the height decreases and gravitational potential decreases, the gpe is converted to kinetic energy of the ball and the presence of air resistance is converted to internal energy of the air molecules

principle conservation of energy

energy cannot be destroyed nor created, it can only be interchanged from one form to another

kinetic energy

Ek = 1/2mv2

gpe

∆Ep = mg∆h

work done

work done is the product of forces and the distance moved in the direction of the force

W=Fd=∆E

Know that radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal

Know that energy is released by nuclear fusion in the Sun

efficiency

(energy output/ energy input) x 100

(power output/power input) x 100

power

work done per unit time or energy transferred per unit time

P= W/t

P= ∆E/t

pressure

force acting per unit time

relationship between pressure and area

as surface are increase, pressure decreases and vice versa

relationship between pressure and force

as force increases, prerssure increases vice versa

how the pressure beneath the surface of a liquid changes with depth

the deeper you go, the greater the pressure

how the pressure beneath the surface of a liquid changes with density of the liquid

the more dense a liquid is the greater the pressure

pressure beneath the surface of a liquid equation

∆p = ρg∆h