WAEC GCE Physics Questions and Answers – 2019 Second Series Expo

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👑 2019 WAEC GCE PHYSICS ANSWERS👑

11-20: BBDBACABDA
31-40: DBBCCBCBCB

SECTION A

(1)
=========================

(2)
H=ut+½gt²
Where H=80m, t=?
80=0(t) + ½(10)(t²)
80=0 + 5t²
80=5t²
80/5=t²
16=t²
t=√16
t=4s

(2b)
Range = U²/g
20²/10
=400/10
=40m

=========================

(3)
F = KAV/L
FL = KAV
K = FL/AV
Where F = ma
= MLT-²
r = M, V = LT-¹
And A = M²

K = MLT-² × M/m² × LT-¹
K = LT-² ×L-¹T-¹
K = T-¹

============================

(5)
(i) Temperature of the body
(ii) Nature of the body
(iii) Distance between the body and the radioactive source
===============================

(6a)
Ferromagnetic materials are those substances which exhibit strong magnetism in the same direction of the field, when a magnetic field is applied to it.

(6b)
(i) Iron
(ii) Nickel
============================

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SECTION B

(8ai)
Pressure is defined as the force acting per unit area on a surface.

(8aii)
Density of liquid.
Depth of point from liquid surface.

(8aiii)
Total pressure = P + pgh
= 75.5cmHg + 1000×10×15
= 75.5cmHg + 150000
= 0.755mHg + 150000
= 150000.755

(8ai)
Pressure is defined as the force acting per unit area on a surface.

(8aii)
Density of liquid.
Depth of point from liquid surface.

(8aiii)
Total pressure = P + pgh
= 75.5cmHg + 1000×10×15
= 75.5cmHg + 150000
= 0.755mHg + 150000
= 150000.755

(8b)
In a tabular form between mass and weight

Under mass
(i) The same everywhere on the earth.
(ii) Scalar quantity.

Under weight
(i) Greater at the poles than at the equator ie it varies.
(ii) Vector quantity.

(8Ci)
(i) Both moving in opposite direction.
(ii) Both moving in the same direction but with one faster than the other.

(8cii)
Given Ma = 0.2kg; Mb = 0.5kg
Va = 5m/s, Vb = 3m/s
Using MaVa + MbVb = V(Ma+Mb)
0.2×(-5) + 0.5×3 = v(0.2 + 0.5)
-1 + 1.5 = 0.7v
0.7v = 0.5
V = 0.5/0.7
Common velocity = 0.71m/s

================================

(11a)
An electric field is a region where an electric force is experienced by a charged body.

(11b)
In a tabular form
Under gravitational potential
(i) Scalar quantity
(ii) Unit is Joule per coulomb

Under gravitational field strength
(i) Vector quantity.
(ii) Unit is Newton per coulomb.

(11ci)
Equivalent capacitance = 5uf//(2uf + 2uf)
= 5uf // 4uf
= 5×4/5+4 uf
= 20/9 uf
= 2.22uf

(11cii)
Total energy stored = 1/2cv²
= 1/2×20/9×10^-6×12×12
=160×10^-6
= 0.00016Joules.

(11di)
Given: Im = 20×10^-3A; V = 25sin100πl
Capacitive reactance Xl = Vm/Im = 25/26×10^-3 = 1250ohms

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(11dii)
1/2πfc = Xl
Where f = 50Hz
1/2×22/7×50c = 1250
314.286c × 1250 = 1
392857 c = 1
C = 1/392857 = 2.545×10^-6F
= 2.545uf

(11e)
A phasor diagram is a graphical way of representing the magnitude and directional relationship between two or more alternating quantities.
=================================

(12a)
Thermoelectrons are electrons emitted at a high temperature such as one produced in a thermionic valve. They are negatively charged.

(12b)
(i) Low voltage battery
Used to heat the heater or heating element.
(ii) Target metal
Used to collect the emitted electrons.

(12Ci)
α – particles has a helium nuclei He while a β-particle has high energy electrons.

(12Cii)
α – particle has a charge of +2e while β-particle has a charge of -e.

(12di)
The radioactive decay law states that the probability per time that a nucleus will decay is constant, independent of time.

(12dii)
(i) Damage to skin.
(ii) Causes cancer.

(12ei)
Given 238 U –> m X + 2α
92 n
= 238 U –> m X + 2 4He
92 n 2
m+(2×4) = 238
m + 8 = 238
m = 238 – 8 = 230
Also
N + (2×2) = 92
N + 4 = 92
N = 92 – 4
n = 88

(12eii)
230
X
88

No of neutrons = 230 – 88 = 142
Neutron – Proton ratio = 142/88 = 1.61

(12eiii)
It is unstable.