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.

41.

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

A.

$$\frac{qBr}{m}$$

B.

$$\frac{mr}{qB}$$

C.

$$\frac{qm}{Br}$$

D.

$$\frac{mq}{r}$$

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

equating F

qvB =  $$\frac{mv^2}{r}$$

qB =   $$\frac{mv}{r}$$

qBr = mv

Therefore, v =   $$\frac{qBr}{m}$$

42.

A body starts with an initial velocity of 20 m/s and moves with a uniform acceleration, a, for 15 seconds. Which of the following equations represents the distance, S, traveled?

A.

300 + 56$$\frac{a}{2}$$

B.

300 + $$\frac{225a}{2}$$

C.

300 + $$\frac{225}{2a}$$

D.

300a + $$\frac{225}{2}$$

u = 20 ms-1, t = 15 s
$$S = ut + 1/2 at^2$$
S = 20(15) + $$\frac{1}{2}× a × 15^2$$
∴ S = 300 + 225$$\frac{a}{2}$$

43.

In a controlled thermal fission reactor, the use of control rods will not affect the

A.

energy generated in the nuclear reactor

B.

rate of production of the neutrons.

C.

speed of the neutrons released on fission.

D.

amount of radiation produced in the nuclear reactor.

In a controlled thermal fission reactor, control rods are used to absorb excess neutrons and thus control the rate of the nuclear reaction. They do not affect the speed of the neutrons released on fission. The speed of the neutrons is determined by the nature of the fission process itself, not by the control rods.

44.

The process of producing electric current by a changing magnetic field is referred to as

A.

magnet induction

B.

electromagnetic induction

C.

D.

electrostatic induction

The process of producing electric current by a changing magnetic field is referred to as electromagnetic induction.

Electromagnetic induction is a phenomenon in which a voltage is generated in a conductor when it is exposed to a changing magnetic field. This voltage can then be used to drive an electric current.

45.

Which of the following diagrams correctly illustrates the mode of oscillation of air in a tube for the first overtone?

A.

A

B.

B

C.

C

D.

D