Mark scheme for IGCSE Physics (0625/3) – Extended Theory May 1999
1
(a)
Distance moved in one revolution is equal to the circumference
= 62.8/63 (in)
Time for 1 rev is 5(s)
Speed = 62.8/5
= 12.6 (m/s)
1
1
1
1
1
4 (max)
(b)(i)
12.6 (m/s) / same value / same number
Direction to the right /east / as marked on diagram
Velocity is a vector or has direction / speed is a scalar or has no direction
P is moving in a circle/constantly changing direction/not in a straight line
If direction changes velocity changes/speed does not or definition of
velocity/speed
1
1
1
1
(c)
Rotation is taking place/direction changing
Force is the centripetal force/force needed for circular motion
Must act through centre otherwise motion not circular
1
1
1
3
(d)(i)
1. Any reference to air resistance
2. The water has hit the ground
1. Velocity on hitting ground = (10 x 0.6) = 6 (m/s)
Distance=6/2 x 0.6
= 1.8 (m)
2. Horizontal distance = average velocity x time or area under graph
= (9.5 x 0.6) = 5.7 (m)
1
1
1
1
1
1
1
7
(ii)
(ii)
2
1
4 (max)
(e)
Water spreads out
1
Cross-sectional area of water at R much larger than at Q
1
Pressure = force/area
1
Same mass/volume/s spread over larger area = Lower pressure or vice versa2
4 (max)
(a)
Heat = mass x specific heat x temperature change
Heat = power x time
Heat from heater = heat in water
30 x l000 x l8 000 = 54000 x c x 2
= 5 000 (J/kg K)
1
1
1
2
1
6
(b)(i)
Most energetic molecules leave the water surface (evaporation)
Carry away extra/latent heat
Water heats air molecules at surface (by conduction)
Air molecules carry heat away by convection
Molecules in water surface emit radiation into air
Energy carried away as wave energy
1
1
1
1
1
1
4 (max)
(ii)
Some of the heat supplied does not end up in the water
Takes longer for same temperature rise
More heat supplied in longer time
1
1
1
7
1
3
(a)
Scale, full size
Line at object height, refracted through lens to pass through focus
Ray through focus produced back to pass through “3 cm line”
Line through centre to locate object and image
Distance of object from lens, 2.5 cm to 2.9 cm
Distance of image from lens ,7.5 cm to 8.7 cm
1
1
1
1
1
1
6
(b)(i)
(ii)
Light of one colour / wavelength / frequency
3 x 108
m/s
Formula quoted sin i / sin r = refractive index
= sin 37o / sin 22o
= 1.5
Beam continued using given angle of refraction (22o)
1
1
1
1
1
1
1
7
Reasonable curve, either direction
Curve to positive plate (upwards)
Electrons are negatively charged
Unlike charges attract
Positive plate attracts electrons
Arrow, towards P, anywhere on the lines PQRS
1
1
Total charge/s = 1013 x 1.6 x 10-19
= 1.6 x 10-6(C)
Charge = current x time
Current = charge/1(s) or 1.6 x 10-6 / 1
Amperes / A
1
1
1
1
1
4 (max)
Equation E = V It or = V q
E = 10000 x 2.1 x 600 (J)
= 1.3x107 (J)
Equation P = E/t
P = 1.3 x l07 /600
2.1 x 104 (W)
1
1
1
1
1
1
6
Path curved, up or down
Curved downwards
Fleming’s (left-hand) rule stated
Current = 12/100
= 0.12 (A)
Bigger deflection
in the opposite direction
1
1
1
1
1
1
1
7
lonisation means creating positively charged and negatively charged ions
from the air molecules between the gauze and the wire
The wire and the gauze are charged, one positively and the other negatively
The ionised air molecules (atoms) move to the opposite charge
Create a “surge” of current seen as a spark
Alpha, a huge amount, any quoted figures
1
1
1
1
1
1
(iii)
(iv)
4
(a)(i)
(ii)
(iii)
(b)(i)
(ii)
(c)(i)
(ii)
(d)(i)
(ii)
(iii)
5
(a)(i)
(ii)
2
2
1
5
(b)
Beta, a small amount compared to alpha, any quoted figures
Gamma, virtually none at all
1
1
6 (max)
Beta:
1
1
1
1
1
1
4 (max)
Gamma :
mass 1/1836 amu/very small/ negligible
constitution 1 electron
charge -1 unit
mass zero
constitution waves/ wave energy
charge zero
3