JAMB Physics Past Questions & Answers - Page 273

1,362.

One of the properties of the earth's magnetic field is that the

A.

north pole lies in the northern hemisphere

B.

geographic and magnetic meridians coincide

C.

earth's magnetic flux is entirely horizontal at a place where the magnetic dip is zero

D.

earth's magnetic flux is entirely vertical at a place where the magnetic dip is zero

Correct answer is C

No explanation has been provided for this answer.

1,363.

A sonometer wire of length 100cm under a tension of 10N, has a frequency of 250Hz. Keeping the length of the wire constant, the tension is adjusted to produce a new frequency of 350Hz. The new tension is

A.

5.1N

B.

7.1N

C.

14.0N

D.

19.6N

Correct answer is D

\(\frac{F_1}{F_2}\) = \(\sqrt\frac{T_1}{T_2}\)

\(\frac{250}{350}\) = \(\sqrt\frac{10}{T_2}\)

T2 = 19.6N

1,364.

An organic pipe closed at one end is 80cm long. Determine the frequency of the fundamental note assuming that the speed of sound in air is 340ms-1

A.

106Hz

B.

213Hz

C.

318Hz

D.

425Hz

Correct answer is A

\(\lambda\) = 4L

= 4 x 80 = 320cm

Converting 320cm to m, we have 3.2m

F = \(\frac{V}{\lambda}\)

= \(\frac{340}{3.2}\)

= 106.25Hz

\(\approxeq\) 106Hz

1,365.

In a resonance tube experiment, the effective length of the air column for the first resonance is 20cm when set into vibration by a tuning fork of frequency 480Hz. Neglecting and effect, the velocity of sound in air is

A.

96ms-1

B.

255ms-1

C.

340ms-1

D.

384ms-1

Correct answer is D

\(\lambda\) = 4(L + C) ; where C = o

\(\lambda\) = 4 x 20 = 80cm

V = \(\lambda\)F

= 80 x 10-2 x 480 = 384ms-1