2019 WAEC PHYSIS THEORY AND OBJECTIVE RUNZ ANSWERS – MAY/JUNE EXPO

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(1)
Mass = 20g = (20/100)kg = 0.02kg
Extension = 5cm = (5/100)m = 0.05m
K = 200N/
V = ?
1/2mv² = 1/2ke²
V = √ke²/m = √200×0.05×0.05/0.02
V = √25
V = 5m/s
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(2a)
P is initial velocity in m/s
β is angle of projection
H is maximum height
R is Range

(2b)
R = P²sin2β/g
at maximum range, sin2β = 1
=> Rmax = p²/g
This happens at β = 45degree
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(3)
(i) Photoelectricity
(ii) Thermonic equation
(iii) Compton effect

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(4)
(i) magnetic declination
(ii) magnetic inclination
(iii) horizontal components

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(8)
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(9ai)
Latent heat is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process.

(9aii)
(i)surface area in contact with atmosphere
(ii)nature of the liquid

(9bi)
The rate of absorption of heat by clay pot is less than the rate of absorption of heat by plastics. Also, water gets evaporated in a clay pot which the evaporation causes cooling; so water in a clay pot remains cool

(9bii)
An increase in pressure in the cooker increase the ambient temperature in the cooker hence the food cooks faster

(9c)
(i) Change in the state of a substance
(ii) Increase in temperature

(9di)
Heat supplied = m1
lvt = m1
12*40*1400=1.5*1
L=12*40*1400/1.5
L=672000/1.5= 448,000J/kg
Laten heat of fusion of the body = 4.48*10^5J/Kg

(9dii)
lvt=mc D tita
12*40*72=1.5*c*60
C=12*40*72/1.5*60
C=384J/Kg/K
Specific heat capacity of the body =384J/Kg/K
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(11)
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Reafreash

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