Year 11 Double Physics- key concepts

what is the unit of speed?

m/s

what is the unit of accelaration?

m/s squared

what is thinking distance

DISTANCE travelled whilst reacting

what is braking distance?

distance travelled after hitting brakes

how do you calculate stopping distance?

thinking distance + braking distance

what factors affect thinking distance?

Alcohol; Drugs; Tiredness

what factors affect braking distance?

Worn tyres; ice/snow; Condition of brakes

what factors affect both thinking and braking distance?

speed

what is meant by the term isotope?

elements with equal numbers of protons but differing numbers of neutrons

why do radioactive emissions occur?

an imbalance between the numbers of protons and neutrons

why is waste from nuclear power stations and nuclear medicine difficult to store?

they are radioactive substances with long half-lives

How can you describe the process of radioactive decay?

random

when doing experimental work with radiation, how can the random nature be accounted for?

repeat reading; measurements made over a long period of time; small variations to be expected as it is random

what is the order of penetrating power for the types of radiation (high to low)?

gamma-beta-alpha

what is the order of ionising power for the types of radiation (high to low)?

alpha-beta-gamma

describe a alpha particle

helium nucleus/ two protons & two neutrons

describe a beta particle

high energy electron

describe gamma radiation

high energy electromagnetic wave

name some natural sources of radiation

cosmic rays; radon gas; rocks/buildings

name some man made sources of radiation

medical uses; nuclear power stations

how does background radiation change at higher altitudes?

there will be more cosmic rays

why does the level of radon gas change vary?

radon comes from rocks, especially granite, so it depends on the amount of granite in the area

how can householders be protected from radon?

good ventilation

what is the half life of a radioactive substance?

the time taken for half the activity/ number of radioactive nuclei to reduce by half

what is newton’s first law?

any body will either remain at rest or at a constant velocity unless a resultant force acts upon it

what is newton’s second law?

resultant force= mass x acceleration

what is newton’s third law?

if a body A exerts a force on body B then body B exerts an equal and opposite force on body A

what is inertia?

the ability of an object to resist a change in motion (things with larger masses have more inertia)

what is ‘g’?

gravitation field stength. it is 10N/kg on earth

what is weight?

the force on an object due to gravity

what is the unit of force?

newtons (N)

what is mass?

the amount of matter in an object

why does an object reach terminal speed?

the air resistance balances out the weight.

what is work done?

energy transferred OR force x distance

what is the unit of work done?

joules (J) OR Nm

what is the energy a body has due to its position?

gravitational potential energy

what is the energy a body has due to its motion?

kinetic energy

if an object obeys Hooke’s law, what happens when a force is applied?

force is proportional to extension

how can energy efficiency of a car be improved?

streamline it; have correctly inflated tyres; stop-start systems; making them lighter

what is the job of an air bag/ crumple zone (in terms of energy)?

increasing the distance over which the energy is transferred so reducing the force.

what is the job of a air bag/ crumple zone (in terms of momentum) ?

the same change in momentum happens over a longer time so there is decreased deceleration as the force decreases

what is the order of the planets ( in terms of increasing distance from the sun)?

mercury-venus-earth-mars-jupiter-saturn-uranus-neptune

which planets are rocky?

mercury-venus-earth-mars

which planets are gaseous?

jupiter-saturn-uranus-neptune

where is there asteroid belt and what does it contain?

between mars and jupite. many rocky asteroids and dwarf planets

how do comets orbit?

highly elliptical orbits

true or false: most planets have moon orbiting around them

true

what is a planetary system?

it compromises a star and all the objects which orbit it

what is a galaxy?

a large collection of stars

what is an A.U.?

An astronomical unit. The mean distance from the sun to the earth.

what is a light year?

the distance light travels in a year

what is the process of generating heat and light in a star called?

nuclear fusion

what is the life cycle of a low mass star?

protostar-main sequence-red supergiant-supernova-neutron star OR black hole

what is the lifecycle of a low mass star?

protostar-main sequence-red giant-white dwarf-brown dwarf

describe how main sequence stars stay stable

radiation pressure = gravitational force

what happens when a star runs short of hydrogen?

it will fuse helium and then other increasingly heavier elements to maintain fusion

why will the star swell when it runs out of hydrogen?

gas and radiation pressure increase as heavier elements are fused

what happens when fusion stops?

gravitational force exceeds the gas and radiation pressure and the star shrinks

what do supernovas create?

elements heavier than iron

how did the solar system begin?

gravitational forces caused matter to get closer creating the sun and plants.