Things Got Wrong On Theory Paper

Question 1

Why is the acceleration of the sled not constant

Answer 1

• mass of sled decreases/changes

- fuel used up

Question 2

What sf to put answer in

Answer 2

• look at question-does it specify
• if not look at figures given
• if not 2-3 sf

Question 3

If piston moves when gas is heated- how does the pressure change?

Answer 3

Remains constant

Question 4

What happens when the temp of gas is increased but volume remains the same

Answer 4

-increased pressure
-more frequent collisions with walls/cylinder/piston
OR
-collide w/ greater force

Question 5

When drawing diffraction what are two rules

Answer 5

• must bend- relative amount to the size of gap and wavelength
• gap between wavefronts after gap must be same as before

Question 6

Why is there a current in the lamp (transformer)? (4mark)

Answer 6

-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

Question 7

Force due to air resistance

Answer 7

Drag-weight

Question 8

Forces acting on skydiver

Answer 8

• air resistance increases (due to parachute being opened)
• air resistance decreases as slows down
• skydiver accelerates constanty as at equilibrium

Question 9

Why does opening the parachute cannot reduce the speed of the skydiver to zero

Answer 9

• skydivers weight still acts

- air resistance requires motion

Question 10

Why are liquids very diff to compress

Answer 10

• liquids made up of molecules that touch

- so strong repulsive force

Question 11

When at boiling point, thermal energy still supplied to water
explain in terms of molecules the effect of this thermal energy on the water

Answer 11

• work done to break bonds

- thermal energy causes some molecules to gain kinetic energy so can leave water as water vapour- evaporation

Question 12

Why does a liquid expand more than a solid when heated

Answer 12

-stronger forces need more energy to break

Question 13

How does range between thermometer with larger bulb with more of liquid and has diff scale compare to normal one

Answer 13

• range is smaller

- more liquid in same tube expands more

Question 14

How does diffraction differ when frequence is increased

Answer 14

• compressions closer toggether

- less diffraction as wavelength is smaller than gap

Question 15

How does emf change in ac generator when handle turned more frequuently

Answer 15

• emf would increase

- frequency of ac would increase

Question 16

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

Answer 16

• tanker float more
• weight tanker must be equal to upward force of water
• depth less- pressure/force on bottom of tanker greater

Question 17

Thermistor resistance

Answer 17

Decreases as temp increases

Question 18

Ldr

Answer 18

Resistance decreases as light intensity increases

Question 19

What type of current does a transformer need

Answer 19

AC- as changing current is needed

Question 20

Why are didgital electronics better than analogue

Answer 20

• carry more info per seond

- maintain quality better over longer distances

Question 21

Brownian motion describe the molecules

Answer 21

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

Question 22

At one point during the fall, she reaches her maximum speed- state her acceleration at this point

Answer 22

0m/s2 (terminal velocity)

Question 23

When at terminal velocity what can be said about the forces acting on her

Answer 23

upward and downward forces equal 
OR no resultant force 
OR forces equal and opposite
 OR forces balanced
OR weight (of body) = tension (in rope)

Question 24

How to calculate speed when dont have time

Answer 24

K.e. Gained= gpe lost
1/2mv2=gpe
Rearrange to find v

Question 25

If did sumersault during diving, would speed on entry to the water change

Answer 25

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

Question 26

Why does a can collapse when the air from it is removed

Answer 26

force/pressure greater on outside surface

Question 27

If repeat thermal heat capacity experiment without using insulation, and obtain higher value for c, explain why

Answer 27

more) thermal energy / heat lost (to surroundings) so temperature rise is less
OR
more thermal energy / heat input required for same temperature rise

Question 28

Why does a balloon burst when temp increases

Answer 28

pressure of air in balloon increases
molecules move faster OR hit balloon surface harder/more often
Larger force breaks rubber
Balloon expands

Question 29

Name the process that causes a potential diff across a solenoid due to the movement of a nearby magnet

Answer 29

Electromagnetic induction

Question 30

Terminal velocity process

Answer 30

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

Question 31

Why is kineti energy diff from gpe

Answer 31

work done against) friction / drag / resistance or thermal energy generated or (displaced) liquid gains gravitational B1 potential energy

Question 32

How liquid and gas differ

Answer 32

molecules close(r)
molecules move only small distances (between collisions) or do not move freely molecules move in clusters or slide past each other

Question 33

How heat travels through metal condutor to outside surface by another processes

Answer 33

shiny surfaces are poor emitters (of radiation)
infrared / radiation / mentioned
less energy lost or lost energy does not need to be supplied

Question 34

Material permenant magnet

Answer 34

Steel

Question 35

Diretion magnetic field

Answer 35

Direction of force on N pole

Question 36

Electron in magnetic field

Answer 36

Deflect into page lhr

Question 37

What is emf

Answer 37

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

Question 38

Conditions required for light to be tir

Answer 38

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)

Question 39

Optical fibres use in telecommunications

Answer 39

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

Question 40

Background radiation

Answer 40

radiation that is always present or due to environment or in everyday life

Question 41

Elastic collisin

Answer 41

Kenetic energy conserved

Question 42

Inelastic collision

Answer 42

• ke not conserved

- transferred to other form such as thermal enegry, elastic potential (eg. Crushing car)

Question 43

Impulse

Answer 43

Force x time