Ordinary level 2025 North West regional mock physics guide

Ordinary level 2025 North West regional mock physics guide

Ordinary level 2025 North West regional mock physics guide

NWRM 2025, 0780 P2 GUIDE
1. a) An equation may be homogeneous yet
incorrect due to
– Presence of a wrong unitless constant(1)
– Absence of an additive term(1)
b) P = 1
2
kρA𝑣𝑥 (1)
equating indices of either m or s gives x = 3 (1)
(6 marks)
2. a) From graph,
Q0 = 56 µC, 1
2
Q0 = 28 µC, (1) Δt = 𝑡1
⁄2= 9s (1)
b) Q = 𝑄0𝑒
-𝑡
𝐶𝑅 ⇒
𝑑𝑄
𝑑𝑡
=
-1
𝐶𝑅
𝑄0𝑒
-𝑡
𝐶𝑅
I = – 𝑑𝑄
𝑑𝑡
⇒ I = 1
𝐶𝑅
𝑄0𝑒
-𝑡
𝐶𝑅 ⇒ I0 = 𝑄0
𝐶𝑅
I0 = 56 𝑥 10-6
9 𝑠
𝐶 (1) ⇒ I0 = 6.2 x 10-6 A (1)
c) C = 18.8 nF, Q0 = CE ⇒ E = 𝑄0
𝐶
E = 56 𝑥 10-6 𝐶
18.8 𝑥 10-6𝐹 (1) ⇒ E = 3.0 V (1)
(6 marks)
3. a) the sources
– must be coherent ie same frequency and
should either be in phase or have a constant
phase difference (1)
– very close to each other (1)
b) λ = 480 x 10-9 m, fringe separation y = 25.6 𝑚𝑚
20
y = 1.28 x 10-3 m, d = 0.4 x 10-3 m but y = 𝜆𝑥
𝑑
⇒
𝑥 =
𝑑𝑦
𝜆 ⇒ 𝑥 =
0.4 𝑥 10-3 𝑥 1.28 𝑥 10-3
480 𝑥 10-9 m (1)
𝑥 = 1.1 𝑚 (1)
𝑐) the fringe separation decreases (1)
λblue < λgreen , from y = 𝜆𝑥
𝑑
, y α λ (1)
(6 marks)
4. a) law of conservation of energy (1)
b) -3 correct equations from Kirchoff’s laws
(1) x 3
– solving the equations simultaneously (1)
– current through 18 Ω resistor = 0.7 A, current
through 5 Ω resistor = 1.4 A, current through
4 Ω resistor = 2.1 A (1)
(6 marks)
5. a)
The string breaks when the oject is vertically below the
centre of the circle as then the tension in the string is
maximum (1)
T – mg = 𝑚𝑣2
𝑟
⇒ 𝑇
𝑚𝑎𝑥 – mg =
𝑚𝑣𝑚𝑎𝑥 2
𝑟
𝑇
𝑚𝑎𝑥 = 62 N, m = 200 g = 0.2 kg, r = 80 cm = 0.8 m
Substitution (1), 𝑣𝑚𝑎𝑥 = 15.5 ms-1 (1)
b) When the string breaks, the particle becomes a
projectile projected horizontally at a speed of 15.5 ms-1
sy = uyt +
1 2
ayt2; sy = -3 m, uy = 0, ay = – 9.8 ms-2
⇒ time to strike the ground t = 0.8 s (1)
𝑣 = 𝑢 + 𝑎𝑡 ⇒ 𝑣𝑥 = 𝑢𝑥 + 𝑎𝑥𝑡, 𝑎𝑥 =0, ⇒ 𝑣𝑥= 15.5 ms-1
𝑣𝑦
= 𝑢
𝑦 + 𝑎𝑦𝑡 ; 𝑢𝑦= 0, 𝑎𝑦 = -𝑔, 𝑡 = 0.8 𝑠
𝑣𝑦
= (-9.8)(0.8) ⇒ 𝑣𝑦 = -7.8 𝑚𝑠-1
v ⃑ = [(15.5)𝐢 – (7.8)𝐣]ms-1 (1)