Mark scheme for IGCSE Physics (0625/3) – Extended Theory May 1999
1(a)Distance moved in one revolution is equal to the circumference1
= 62.8/63 (in)1
Time for 1 rev is 5(s)1
Speed = 62.8/51
= 12.6 (m/s)1
4 (max)
(b)(i)12.6 (m/s) / same value / same number1
Direction to the right /east / as marked on diagram1
(ii)Velocity is a vector or has direction / speed is a scalar or has no direction1
P is moving in a circle/constantly changing direction/not in a straight line1
If direction changes velocity changes/speed does not or definition of
velocity/speed1
4 (max)
(c)Rotation is taking place/direction changing1
Force is the centripetal force/force needed for circular motion1
Must act through centre otherwise motion not circular1
3
(d)(i)1. Any reference to air resistance1
2. The water has hit the ground1
(ii)1. Velocity on hitting ground = (10 x 0.6) = 6 (m/s)1
Distance=6/2 x 0.61
= 1.8 (m)1
2. Horizontal distance = average velocity x time or area under graph1
= (9.5 x 0.6) = 5.7 (m)1
7
(e)Water spreads out1
Cross-sectional area of water at R much larger than at Q1
Pressure = force/area1
Same mass/volume/s spread over larger area = Lower pressure or vice versa2
4 (max)
2(a)Heat = mass x specific heat x temperature change1
Heat = power x time1
Heat from heater = heat in water1
30 x l000 x l8 000 = 54000 x c x 22
= 5 000 (J/kg K)1
6
(b)(i)Most energetic molecules leave the water surface (evaporation)1
Carry away extra/latent heat1
Water heats air molecules at surface (by conduction)1
Air molecules carry heat away by convection1
Molecules in water surface emit radiation into air1
Energy carried away as wave energy1
4 (max)
(ii)Some of the heat supplied does not end up in the water1
Takes longer for same temperature rise1
More heat supplied in longer time1
7
3(a)Scale, full size1
Line at object height, refracted through lens to pass through focus1
Ray through focus produced back to pass through “3 cm line”1
Line through centre to locate object and image1
Distance of object from lens, 2.5 cm to 2.9 cm1
Distance of image from lens ,7.5 cm to 8.7 cm1
6
(b)(i)Light of one colour / wavelength / frequency1
(ii)3 x 1081
m/s1
(iii) Formula quoted sin i / sin r = refractive index1
= sin 37o / sin 22o1
= 1.51
(iv) Beam continued using given angle of refraction (22o)1
7
4(a)(i)Reasonable curve, either direction 1
Curve to positive plate (upwards)1
(ii)Electrons are negatively charged
Unlike charges attract
Positive plate attracts electrons2
(iii) Arrow, towards P, anywhere on the lines PQRS1
5
(b)(i)Total charge/s = 1013 x 1.6 x 10-191
= 1.6 x 10-6(C) 1
(ii)Charge = current x time1
Current = charge/1(s) or 1.6 x 10-6 / 11
Amperes / A1
4 (max)
(c)(i) Equation E = V It or = V q1
E = 10000 x 2.1 x 600 (J)1
= 1.3x107 (J)1
(ii)Equation P = E/t1
P = 1.3 x l07 /6001
2.1 x 104 (W)1
6
(d)(i)Path curved, up or down1
Curved downwards1
Fleming’s (left-hand) rule stated1
(ii)Current = 12/1001
= 0.12 (A)1
(iii) Bigger deflection1
in the opposite direction 1
7
5(a)(i)lonisation means creating positively charged and negatively charged ions1
from the air molecules between the gauze and the wire1
The wire and the gauze are charged, one positively and the other negatively1
The ionised air molecules (atoms) move to the opposite charge1
Create a “surge” of current seen as a spark1
(ii)Alpha, a huge amount, any quoted figures1
Beta, a small amount compared to alpha, any quoted figures1
Gamma, virtually none at all1
6 (max)
(b) Beta: mass 1/1836 amu/very small/ negligible1
constitution 1 electron1
charge -1 unit1
Gamma : mass zero1
constitution waves/ wave energy1
charge zero1
4 (max)
1