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JAMB Physics Past Questions & Answers - Page 154

766.

The r.m.s value of a supply voltage is quoted at 200v. What is the approximate peak value of the voltage?

A.

200volts

B.

300volts

C.

283volts

D.

250volts

Correct answer is C

Vr.m.s = V0 ÷ V2, where Vr.m.s rep. to as voltage root –square mean, v = peak voltage

Vr.m.s = 200volt, v = ?

200 = V0 ÷ V2

V0 = 200v2

= 200 × 1.414

= 282.8 volts V0 = b &approx.; 283 volts

767.

A good electric cell should have the following except

A.

A minimum of polarization effect

B.

A long life

C.

A cheap and safe electrolytes

D.

Cost and dangerous of the cell

Correct answer is D

A good electric cell should proses the following

1. A long life of an electric cell,

2. A minimum of polarization effect

3. A cheap and safe electrolytes

Except D cost and dangerous of the electric cell

768.

The dimension of universal gravitational constant is……….?

A.

M­^{–1}L^3 T^{–2}

B.

ML3T2

C.

ML3

D.

MLT-2

Correct answer is A

f α (MM ÷g2)

F(GMM ÷ r2) [G – gravitational constant]

GMM = Fr2

G = F02 ÷ MM = m × aπr2 ÷ MM (f = ma)

= (m × m5-2 × r2) ÷ MM

= (Kg.m52 × m2) ÷ Kg.Kg

=1 ÷ kg.m3.52

The dimension mathematically representation have a quantities of M, L AND T

M (Mass) = kg, L (Length) = M, T (Time) second

G = kg-1 m2.52(Using dimension rule)

M-1.L3.T-2

∴ The universal gravitational constant (G) = M­^{–1}L^3 T^{–2}

769.

What is the S.I unit of relative density?

A.

kg m-2

B.

kg m2

C.

kg cm3

D.

has no S.I unit

Correct answer is D

Note: relative density has no S.I unit

∴ Relative density = weight of substance ÷ weight of equal volume of water

RD = w1 ÷ (w1 – w2) (no S. I unit)

770.

If a projectile has maximum range of 36m, find the speed of projection (Take g = 9.8m/s2)

A.

19m/s

B.

2m/s

C.

4m/s2

D.

7m/s2

Correct answer is A

No explanation has been provided for this answer.