** WAEC 2019 physics answers**

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**Complete No 10🖕**

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**ANSWERS LOADING…….100℅**

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**Physhs-Obj**

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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**

**=========================**

**Question 2.**

**a)**

**P is initial velocity in m/s**

**β is angle of projection**

**H is maximum height **

**R is Range**

**b)**

**R = P^2sin2β/g**

**at maximum range, sin2β = 1**

**=> Rmax = p^2/g**

**This happens at β = 45degree**

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**(3)**

**(i) magnetic declination**

**(ii) magnetic inclination**

**(iii) horizontal components**

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**(4)**

**(i)Magnetic Declination**

**(ii)Horizontal Component of Earth’s Magnetic Field**

**(iii)The angle of Dip or Magnetic Inclination**

**(5a)**

**Free electrons are electrons in a material which can contribute to electric current.**

**(5b)**

**hole is the absence of an electron in a particular place in an atom**

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**Q1, 2, 3, 4, 5👆👆👆👆**

**(5)**

**Draw the diagram**

**Using cosine law **

**Cos∅ = 16²+10²-14²/2(16)(10)**

**Cos∅ = 256 + 100 – 196/320**

**Cos∅ = 160/320**

**Cos∅ = 0.5**

**∅ = cos-¹(0.5)**

**∅ = 60°**

**Angle between 10N and 16N **

**= 180 – ∅ (sum of angles on a straight line)**

**= 180 – 60**

**=120°**

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**(6a)**

**Principle of operation of fiber optics state that the density of transparent glass and the refractive index is greater than the density of the two mirrors**

**(6b)**

**(i)it is used to view deep down the throat of a patient**

**(ii)it is used to conveying information**

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**.**

**(8ai)**

**It state that every particles in the universe attract every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them**

**(8aii)**

**Gravitational field is a region of space around a mass on which the gravitational force of the mass can be felt**

**(8bi)**

**F=GMeM/re² ——from newton’s law**

**Where Me is mass of earth**

**re is the distance of mass from earth**

**G is a constant of gravitation **

**But F=GMeM/re² =mg**

**Me=GMe/re²=g**

**g=GMe/re²**

**(8bii)**

**(i)That The earth is a sphere**

**(ii)That g depends on mass of earth alone**

**(8c)**

**Using F = GMeM/r²**

**F=6.67*10^-11*5.98*10²4*2.00*10³degree/(1.50*10^8*10³)²**

**F= 79.7732*10^43/2.25*10²²**

**F=35.455*10²1**

**=3.5455*10²2N**

**(8di)**

**Escape velocity (Ve) is the minimum velocity required for an object (egg statelite) to just escape or leave the gravitational influence or field of an astronomical body (eg earth) permanently **

**(8dii)**

**(i)g varies across the earth but G is constant **

**(ii)the unit of g is m/s² while that of G is NM²/Kg²**

**=**

**(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**

**(11ai)**

**Force is anything that causes motion.Its S.I unit is Newton(N) or Kgm/s^2**

**(11aii)**

**(i) Static friction**

**(ii) Dynamic friction**

**(11bi)**

**DRAW THE GRAPH**

**(11bii)**

**Deceleration**

**during last 5s=18/5=3.6m/s^2**

**(11biii)**

**Total distance=S1+S2+S3+S4**

**=(30*20)+1/2(18+30)(6)+(18*10)=(1/2*5*18)**

**=600+144+180+45**

**=969metres**

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