# 2018 Waec Gce Physics Theory & Obj Answers [expo]

Physics – Obj

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(1a)

Young modulus of a material or the modulus of elasticity.

(1b)

Potential Energy to kinetic Energy.

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(2)

e = 0.7m

m=60 × 10^-3kg = 6.0×10^-2kg

K = 200Nm^-1

W = 1/2ke² = 1/2mv²

1/2ke² = 1/2mv²

V² = ke²/m = 200×0.7²/6.0×10^-2

V² = 98×10²/6

V² = 16.33×10²

V = √1633

V = 40.4

Speed = 40.4ms^-1

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(3)

(i) Optical fibres have extremely high bandwidth

(ii) They have longer transmission distance

(iii) They have resistance to electromagnetic interference

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(4a)

It is used in geometric stations used to move a satellite from low earth orbit into a geostationary orbit.

(4b)

Polar orbit satellite is used in earth mapping.

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(5a)

(i) Centripetal force

(ii) Centrifugal force

(5b)

Ft = mDv

where F = force

t = time

Dv = change in velocity

m = mass of object

Hence F = mDv/t

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(6a)

(i) It can cause short and long term sun burn effects.

(ii)It can cause blindness when flashed to the eyes.

(6b) Energy = hf

= 6.60×10^-34 × 4.82×10^14

= 3.18×10^-19J

= 1.99ev

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(7)

V = 2πR/T

R = 9.6×10^6 + 6.4×10^6 =16×10^6 m

T = 24hrs =(24×60×60)s

V = 2×3.142×16×10^6/24×60×60

V = 1162.96m/s

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8a) Mass is the amount of material contained in a body and the SI unit is Kg while Weight is the force exerted on a body by the gravity of the object. ..Mass is a scalar quantity( It has not specific direction), While Foce is a vector quantity (Its in the same direction with gravity)

8ai

Mass is measured in Kg

Weight is measured in Newton

Mass is a scalar quantity

Weight is a vector quantity

Mass is constant

Weight varies

8aii) Clockwise moment about the pivot.

Moment = Force x Distance

Moment = 250 x 0.75

Moment = 187.5Nm

8bii (the value of F)

Clockwise moment = Anti clockwise moment

Fx(1.5+0.75) + 50x 0.75 = 250 x 0.75

F x 2.25 + 37.5 = 187.5

2.25F = 187.5-37.5

2.25F= 150

F = 150/2.25

F= 170.83N