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Physics > Physics but Shorter > Flashcards

Physics but Shorter Flashcards

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1
Q

Define inertia

A

How hard it is to change the motion of an object

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2
Q

State Newton’s First Law

A

A body will remain at rest, or continue to move with a constant velocity unless acted upon by an external (resultant) force

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3
Q

Resultant force definition

A

The total force acting upon an object

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4
Q

Newton’s Second Law

A

Resultant force = mass x acceleration (this means that acceleration is directly proportional to resultant force)

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5
Q

Define weight and mass

A

Weight - the measure of how large the force of gravity is on an object (N)
Mass - the measure of how much matter an object has (kg)

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6
Q

What is Newton’s Third Law

A

If object A exerts a force on object B, object B also exerts an equal and opposite force on object A.

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7
Q

What kind of energy is kinetic energy

A

Movement energy - faster objects have more kinetic energy

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8
Q

How is energy taken away from KE and GPE

A

It becomes friction (work done)

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9
Q

State Hooke’s Law

A

The extension of a material is directly proportional to the force applied

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10
Q

How is work done represented

A

As the area under a force extension graph

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11
Q

What are the ways vehicles lose energy and what are the ways to improve them

A
  • Aerodynamic losses: more streamlined
  • Rolling resistance: correctly inflated tyres from right material
  • Idling losses: stop-start systems turn off the engine in traffic
  • Inertial losses: lighter car (carbon fibre, not heavy metal)
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12
Q

Car safety features

A
  • Seat belt
  • Crumple zone
  • Air bag
  • Side-impact bars (strong bars inside car doors)
  • Passenger cell (a rigid cage around passengers)
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13
Q

What do car safety features do

A

They slow the passengers down as gradually as possible which means the force also decreases - they also increase the distance over which energy is transferred (force=work done/distance)

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14
Q

Momentum fact file

A
  • Momentum is the amount of motion an object has
  • Measured in kgm/s
  • Total momentum before interaction = total momentum after interaction
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15
Q

Two words relating to kinetic energy in car crashes

A

Elastic collision and inelastic collision (inelastic means kinetic energy is lost)

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16
Q

What accelaration is given by gravity

A

10m/s squared, so if an object is thrown up this becomes -10

17
Q

Moment fact file

A
  • A moment is the turning effect of a force
  • Moment = force x distance to the pivot
  • The sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments about the same point
  • When the moments of each side are balanced they are in equilibrium
18
Q

What is an astronomical unit

A

The mean distance from the earth to the sun

19
Q

Give the main stages of the life cycle of a star

A
  • Protostar
  • Main sequence
  • Red giant
  • White dwarf
    OR
  • Red supergiant
  • Supernova
  • Black hole / neutron star
20
Q

What creates outwards pressure in stars

A

Gas and radiation pressure

21
Q

Two types of evidence for the big bang

A
  • Cosmological red shift
  • Cosmic microwave background radiation
22
Q

Key terms for cosmological red shift

A
  • Continuous spectra: a full rainbow of light
  • Absorption spectra: a continuous spectra that’s been blocked
23
Q

Why are the waves in CMBR microwaves

A

Because they’ve stretched from the original gamma rays

24
Q

How does a galaxy’s distance from us correlate with red shift?

A

The further away it is the greater the redshift

25
Q

Define isotope

A

Atoms of the same element which have the same number of protons but a different number of neutrons

26
Q

Define ionising

A

When radiation interacts with cells and damages DNA (cancer)

27
Q

Alpha fact file

A
  • Its symbol is below
  • It is a helium nucleus
  • It can be stopped by a thin sheet of paper or a few cm of air
  • It’s very damaging to the body
28
Q

Beta fact file

A
  • Its symbol is below
  • It is a fast moving and high energy electron
  • Can be stopped by a few mm or aluminium or 1m air
29
Q

Gamma fact file

A
  • Only stopped by several cm of lead or very thick concrete, so passes easily through the body
30
Q

What is the process for storing nuclear waste

A
  • It’s first cooled in large water tanks
  • It’s turned into a type of glass so it can’t flow
  • It’s placed inside steel drums and sealed in concrete
    • It’s buried deep underground
31
Q

Radon gas factfile

A
  • It emits alpha
  • It goes from uranium to radium, radon and polonium
  • Because radon is a gas it can be breathed in
    • Cornwall has the highest concentration
32
Q

What is activity and what is it measured in

A

It’s the measure of decays per second and measured in becquerels - also known as the count rate

33
Q

What happens in a nuclear fission power station

A
  • Uranium -235 in fuel rods absorbs a slow moving neutron which makes it unstable
  • The uranium decays and splits into two smaller nuclei, and a large amount of energy is released
  • These neutrons cause more atoms to undergo fission
    • This is a chain reaction
34
Q

Name features used in the reactor to stop out of control chain reactions

A
  • The moderator slows down neutrons (this is either water or graphite rods)
  • Boron control rods are dropped into the reactor to slow the reaction - they absorb extra neutrons
  • The reactor is surrounded by concrete
    • Water acts as a coolant
35
Q

What would nuclear fusion involve and where would we get the fuel

A

Two isotopes of hydrogen making helium, taken from sea water

36
Q

Which laboratory is most advanced for fusion and what does it involve

A

The JET laboratory which has a doughnut shaped reactor where the particles are accelerated into each other

Physics (7 decks)

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