S2 T4 Physics EOT

Scalar quantities

Quantities that only have magnitude

• Temperature

• Mass

• Distance

Vector

Quantities with both magnitude and direction

• Displacement

• Force

• Velocity

Displacement

Straight line distance between finishing and starting points

Specifies direction of end point and starting point

Speed

Measure of how fast something moves

Average speed

A measure of how fast something moves overall.

→ Ignores stops and changes, assumes object was travelling at same speed the whole time.

Instantaneous speed

Speed at a particular instant

→ shown on speedometer

Ticker timer speeds

Speed conversions

Distance-Time graphs

Show how far an object travels as time progresses

Flat line → Motion has stopped

Steep slope → covers greater distance

Gradient = objects average speed over a time interval

distance on vertical axis

Displacement-time

Displacement is on vertical axis

Speed-time graphs

flat line = constant

increase = graph rising upwards

descrease = graph falling downwards

Acceleration

a measure of how quickly a change of speed occurs

a = v-u/t

gravitational acceleration

an object near the surface of the Earth falls with an acceleration of 9.8 m/s/s

linear acceleration

v = u+at.

Newton’s first law

An object at rest will remain at rest unless acted upon by a force

An object that is moving will continue to move at the same speed + direction unless an unbalanced force acts upon it

types of forces

balanced: all of the forces acting are equal in size but opposite in direction, then balanced.

balanced → motion doesn’t change

rested → stationary

unbalanced → speeds up, slows down, change direction

force that is not balanced acts on an object then the motion of the object will change.

examples of first law

When a train begins to move, your feet move forwards with it. However, your body tends to remain stationary, making it appear as if you are ‘falling backwards

first law relation to car safety

travelling in car at 60km/h and stops, you will continue to travel forward at 60km/h. seatbelts restrainbody so that u will stop with the car

air bag reduces the force on a passenger in a collision and prevents their head hitting the stering wheel or side of the car

inertia

the tendency to resist any change in motion is called an objects inertia

increaseased msss → greater inertia, harder it is to change

Newton’s second law

• acceleration directly proportional to the net force acting on it and inversely proportional to its mass

examples of newtons second law

Pushing a car and a truck.

truck is heavier therefore requires more force. trcuk will accelerate less

to calculate net force

f = ma

f on top

m on bottom left

a on bottom right

Newton’s third law

For every action force there is an equal and opposite reaction force

example of newtons third law

forces always occur in pairs

tennis ball hit by raquet.

force that racquet applies to tennis ball is aactionforce

the force that the ball applies to the racquet is called a reaction force

kinetic energy

energy of a moving object

depends of mass and speed.

mass doubles → energy doubles

speed doubles → energy increase by factor of 4

kinetic energy relation to car safety

in collision, energy is transferred to other objects or transformed into other forms of energy

heavier vehicle and greater the speed, more energy transferred and more damage

cars travelling at higher speed need longer distances to brake and stop.

potential energy

energy that an object has because of it's position or structure. oftenc called stored energy

gravitational potential energy

an object positioned above the ground has it.

higher above the ground = greater gravitational energy

greater mass = greater potential energy

energy efficiency

useful energy output/total energy input x 100

kinetic energy formula

½ mass * speed ²

Ek is measured in J, Mass is measured in kg and speed is measured in m/s

GRAVITATIONAL POTENTIAL ENERGY FORMULA

mass * acceleration due to gravity * height

gravity is 9.8 N/Kg

conservation of energy

energy may be transferred from one object to another, but is never created or destroyed.

acceleration

the rate of change of velocity

(v-u)/t

air resistance

the retarding force (drag) caused by collisions between air and moving objects (friction)

average speed

the ratio of distance travelled to time taken (scalar)

displacement

an objects change in position due to it starting position and final position. straight line connecting start and end points specified in terms of length and direction

distance

a measurement of how far an object travels during a parrticular mtion or journey

efficiency

the percentage of energy that is effectively transformed by a system. A measure of useful energy output of an energy transfer

elastic potential energy

energy stored in a stretched or compressed material such as a spring

free fall

motion where gravity is the only force acting on the body

gravitational potential

hte potential energy available to an object due to its position in a gravitational field

law of conservation of energy

the energy in a system before an interaction is exactly equal to the energy in a system after the interaction

magnitude

the size or extent of something, with no need for direction. A quantitative measure expressed as a number of a standard unit

mechanical energy

the energy that a body possesses due to its position or motion.

kinetic energy, gravitational energy and eleastic postential energy

velocity

the ratio of displacement to time taken (vector)

speed of an object tin a given direction

terminal velocity

the final velocity at which an object falls, with no further acceleration possible due to air resistance

speed distance time triangle

converting between km/h and m/s

divide by 3.6 to go from km/h to m/s

times by 3.6 to go from m/s to km/h