2021 WAEC Physics Objective obj Essay Answer

2021 WAEC Physics Objective obj Essay Question And Answer

WAEC Physics questions and answers

Objective answer

1-10: DACAACBBCC

11-20: BDBABBACAC

21-30: BCBACBBACA

31-40: BDDDDACCCA

41-50: AAAABBCBBC

Essay answers

(1)
Original length Lo= 3m
Extension e = 310 = 3*3= 9m

F×e
F=ke where k = 982.3NM-²
F=982.3*9=8,840.7N

The five that produce the extension F = 8.840.7N

(2a)
Flat metal plate are mainly used to collect heat for space heating in solar panels for heat transfer.

(2b)
Thermal insulator is used for reduction of heat transfer between objects in thermal contact

(2c)
tubes is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.

(3a)
highly purified silica glass.

(3b)
To confine the optical signal in the core the refractive index of the core must be greater than that of the cladding.

(5)
Escape velocity = VE
Radius of the earth = R

Acceleration due to gravity = 10ms²
Escape velocity Be=√2R

VE=√2*10R
VE=√20R

(6)
Angle at horizontal θ = 30°
Time of light , T = 25sec

Velocity of projection u = ?
But T=2using sinθ/g

25= 2u*sin30/10
25=0.5u/5

0.5u=125
U=125/0.5

=250ms-¹

(7)
(i)Coherence

(ii)Directionality
(iii)Monochromatic

(8ai)
A torque is defined as a measure of the force that can cause an object to rotate about an axis

WAEC Physics Questions 2021 and Answers
(8aii)

Factors that determine torque are;
– The magnitude of the force

– The radius
– The angle between the force and the lever arm

(8bi)
Free fall simply means the act of which are objects fall freely under the influence of gravitational force. An object under free fall does not encounter air resistance

(8bii)
Height of tower H = 40.0m
Velocity v = 10.0m/s, time t= ? , g=10.0m/s

Using the relation
S= ut + 1/2gt^2

H= ut + 1/2gt^2
40= 10t + 1/2*10t^2
4= t + t^2/2

= t^2 + 2t – 8=0 ( solving quadratically)
= (t+4)(t-2)=0

t+4=0 or t-2=0
t= -4 or t=2

Therefore time to fall on the ground t=2s

(8c)
R.d of oil =R1 = 0.72

R.d of water = R2=1.00

R.d of liquid= R1/R2= 0.72/1 = 0.72

R.d = density of wood(P1)/density of water(P2)
0.72=P1/1.00

P1= 0.72*1.00=0.72g/cm³
But density of wood= mass of wood/volume of wood

0.72= mass of wood/8*8*8
Mass of wood = 0.72*512 = 368.64g

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