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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.

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36.

A 100 kg device is pulled up a plane inclined at 30° to the horizontal with a force of 1000 N. If the coefficient of friction between the device and the surface is 0.25, determine the total force opposing the motion.
[ g = 10 ms-2]

283.5N

975.0N

216.5N

716.5N

View answer & explanation

Correct answer is D

The forces opposing the motion of the device are "mgsin θ" and "μN" where N is the normal reaction
From the diagram, on resolving to components, N = mgcos θ
Total opposing force = mgsin θ + μmgcos θ = mg(sin θ + μcos θ)
= 100 × 10 × (sin 30° + 0.25 × cos 30°)
= 1000 × (0.5 + 0.2165)
= 1000 × 0.7165
= 716.5 N

37.

The most appropriate value of fuse for a kettle rated 220 V, 1.06 kW is

View answer & explanation

Correct answer is C

V = 220V, P = 1.60KW = 1060W, I = ?

P = IV

I = $\frac{P}{V} = \frac{1060}{220}$

≈ 5A.

38.

A planet has mass, M, and radius R, If the universal gravitational constant is G, what is the expression for the escape velocity of an object on the planet?

$\frac{\sqrt{GR}}{2}$

$\frac{\sqrt{2GM}}{R}$

$\frac{\sqrt{2G}}{R}$

$\frac{\sqrt{GM}}{R}$

View answer & explanation

Correct answer is B

The expression for the escape velocity $v_e$ of an object from a planet of mass M and radius R using the universal gravitational constant G is:

$v_e = \frac{\sqrt{2GM}}{R}$

39.

Increasing the frequency of a sound wave produces a sound with

higher pitch

longer wavelength

more overtones

reduced loudness

View answer & explanation

Correct answer is A

The pitch of a sound is determined by its frequency. Higher frequencies correspond to higher pitches. For example, a high-pitched sound like a whistle has a higher frequency than a low-pitched sound like a drum.

40.

In a mass spectrometer, an ion of charge, q, and mass, m, moving in a path of radius, r, in a field of flux density, B, has a speed of

$\frac{qBr}{m}$

$\frac{mr}{qB}$

$\frac{qm}{Br}$

$\frac{mq}{r}$

View answer & explanation

Correct answer is A

F = qvB ( force on moving charge in a magnetic field) F = $\frac{mv^2}{r}$

equating F

qvB = $\frac{mv^2}{r}$

qB = $\frac{mv}{r}$