Things Got Wrong On Theory Paper Flashcards
Why is the acceleration of the sled not constant
- mass of sled decreases/changes
- fuel used up
What sf to put answer in
- look at question-does it specify
- if not look at figures given
- if not 2-3 sf
If piston moves when gas is heated- how does the pressure change?
Remains constant
What happens when the temp of gas is increased but volume remains the same
-increased pressure
-more frequent collisions with walls/cylinder/piston
OR
-collide w/ greater force
When drawing diffraction what are two rules
- must bend- relative amount to the size of gap and wavelength
- gap between wavefronts after gap must be same as before
Why is there a current in the lamp (transformer)? (4mark)
-ac caused magnetic field in core/iron
-magnetic field alternates
-field cut with secondary coil
-emf enduced (and current flows in lamp)
OR
-induced current in lamp
Force due to air resistance
Drag-weight
Forces acting on skydiver
- air resistance increases (due to parachute being opened)
- air resistance decreases as slows down
- skydiver accelerates constanty as at equilibrium
Why does opening the parachute cannot reduce the speed of the skydiver to zero
- skydivers weight still acts
- air resistance requires motion
Why are liquids very diff to compress
- liquids made up of molecules that touch
- so strong repulsive force
When at boiling point, thermal energy still supplied to water
explain in terms of molecules the effect of this thermal energy on the water
- work done to break bonds
- thermal energy causes some molecules to gain kinetic energy so can leave water as water vapour- evaporation
Why does a liquid expand more than a solid when heated
-stronger forces need more energy to break
How does range between thermometer with larger bulb with more of liquid and has diff scale compare to normal one
- range is smaller
- more liquid in same tube expands more
How does diffraction differ when frequence is increased
- compressions closer toggether
- less diffraction as wavelength is smaller than gap
How does emf change in ac generator when handle turned more frequuently
- emf would increase
- frequency of ac would increase
Boat sails on calm sea- density of sea water greater than density of river water
state and explain change. In depth of bottom of tanker below the surface of the water
- tanker float more
- weight tanker must be equal to upward force of water
- depth less- pressure/force on bottom of tanker greater
Thermistor resistance
Decreases as temp increases
Ldr
Resistance decreases as light intensity increases
What type of current does a transformer need
AC- as changing current is needed
Why are didgital electronics better than analogue
- carry more info per seond
- maintain quality better over longer distances
Brownian motion describe the molecules
Smoke particles
- random - sudden changedirection/zig-zag motion - appear/disappear from view/go out of come into focus
Air molecules
- collide smoke particles - aire molecules faster/smaller/lighter - move randomly
At one point during the fall, she reaches her maximum speed- state her acceleration at this point
0m/s2 (terminal velocity)
When at terminal velocity what can be said about the forces acting on her
upward and downward forces equal OR no resultant force OR forces equal and opposite OR forces balanced OR weight (of body) = tension (in rope)
How to calculate speed when dont have time
K.e. Gained= gpe lost
1/2mv2=gpe
Rearrange to find v
If did sumersault during diving, would speed on entry to the water change
speedisthesame B1 EITHER
loss in g.p.e. is the same B1 k.e. gained is the same B1 OR
acceleration is the same (B1) distance fallen is the same
Why does a can collapse when the air from it is removed
force/pressure greater on outside surface
If repeat thermal heat capacity experiment without using insulation, and obtain higher value for c, explain why
more) thermal energy / heat lost (to surroundings) so temperature rise is less
OR
more thermal energy / heat input required for same temperature rise
Why does a balloon burst when temp increases
pressure of air in balloon increases
molecules move faster OR hit balloon surface harder/more often
Larger force breaks rubber
Balloon expands
Name the process that causes a potential diff across a solenoid due to the movement of a nearby magnet
Electromagnetic induction
Terminal velocity process
initial) acceleration caused by weight / force of gravity
• acceleration decreases
• drag / resistance force increases (with speed)
• (finally / at terminal velocity) no acceleration / constant speed
• (finally / at terminal velocity) no resultant force
Why is kineti energy diff from gpe
work done against) friction / drag / resistance or thermal energy generated or (displaced) liquid gains gravitational B1 potential energy
How liquid and gas differ
molecules close(r) molecules move only small distances (between collisions) or do not move freely molecules move in clusters or slide past each other
How heat travels through metal condutor to outside surface by another processes
shiny surfaces are poor emitters (of radiation)
infrared / radiation / mentioned
less energy lost or lost energy does not need to be supplied
Material permenant magnet
Steel
Diretion magnetic field
Direction of force on N pole
Electron in magnetic field
Deflect into page lhr
What is emf
energy supplied in driving charge in a circuit / conductor or property of source / battery / cell / power supply
energy supplied per / to unit charge or energy transferred to electrical energy or from other form of energy or energy in driving charge around a complete circuit
Conditions required for light to be tir
light (must pass) from medium where it travels slower or to medium where it is faster or from medium with larger B1 refractive index or to medium with smaller refractive index
angle of incidence (must be) greater than the critical angle / sin–1(1 ÷ n)
Optical fibres use in telecommunications
light / infrared travels in fibre
total internal reflection at inner surface or within (graded-index) fibre
light carries information / signal / data / message or signal / light encoded
Background radiation
radiation that is always present or due to environment or in everyday life
Elastic collisin
Kenetic energy conserved
Inelastic collision
- ke not conserved
- transferred to other form such as thermal enegry, elastic potential (eg. Crushing car)
Impulse
Force x time
