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Physics questions and answers

Physics Questions and Answers

If you want to learn more about the nature and properties of matter and energy or you're simply preparing for a Physics exam, these Physics past questions and answers are ideal for you.

227.

Which of the following statements about the universal gravitational constant, G, is true? 

A.

It is fundamental quantity

B.

It has dimension M-¹L³T-²

C.

Its S.I. unit is N m2kg

D.

It is a vector quantity

Correct answer is B

The universal Gravitational constant(G) is a scalar quantity as it is not in a particular direction

dimensional formula =M-¹L³T-²

S.I. unit = Nm2/kg2

228.

A current of 2A passes through a wire of resistance 4Ω for 3 minutes. Calculate the energy lost

A.

960J

B.

1440J

C.

2880J

D.

48J

Correct answer is C

Power = current[I]2 * Resistance[R] → 22 * 4 → 4 * 4 = 16watts

time = 3minutes → 3 * 60 = 180s

Energy = power * time → 16 * 180 = 2880j

229.

The diagram above is an illustration of an a.c. circuit.Calculate the reactance of the capacitor.

A.

2016Ω

B.

2000Ω

C.

200Ω

D.

4000Ω

Correct answer is C

Capacitive reactance, XC = \(\frac{1}{2πFC}\) → \(\frac{1}{2π * 500/π * 5 * 10^{-6}}\)

10.005 → 200Ω

230.

Which of the following statements is an effect of compressing gas molecules at constant temperature? 

A.

The pressure on the molecules decreases.

B.

The molecules gain more kinetic energy

C.

The molecules make more impact per second on the walls of the container

D.

The molecules increase in size

Correct answer is C

More collisions mean more force, so the pressure will increase. 

When the volume decreases, the pressure increases.

This shows that the pressure of a gas is inversely proportional to its volume.

This is shown by  Boyle's law.