JAMB Physics Past Questions & Answers - Page 166

826.

Body floats in fluid when its …………………

A.

Displaces its own volume of the liquid (fluid)

B.

Displaces its own weight of the fluid

C.

Displace its own density of the fluid

D.

Is no longer subjected to gravity

Correct answer is B

Note:The principle of floatation states that a floating body displaces its own weight of the fluid or which its float.

For object to sink weight of the object (W) > upthrust of the fluid (v) i.e. w > u

(i.e. weight of the body (or object) mass of the fluid)

There is an explanation video available below.

827.

A sonometer wire under a tension of N10N, produces a frequency of 250Hz when plucked. Keeping the length of the wire constant, the tension is adjusted to produce a new frequency of 350Hz. Calculate the new tension

A.

39.2N

B.

19.6N

C.

14.2N

D.

7.4N

E.

5.1N

Correct answer is B

f \(\alpha\) \(\sqrt{T}\)

\(\frac{f_1}{f_2} = \sqrt{\frac{T_1}{T_2}}\)

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

\(\frac{5}{7} = \sqrt{\frac{10}{T_2}}\)

\(\frac{25}{49} = \frac{10}{T_2}\)

T2 = \(\frac{49 \times 10}{25} = 19.6\)

828.

What is the image distance of an object placed at a distance of 2f from a converging lens of focal length f?

A.

f/4

B.

f/2

C.

f

D.

2f

E.

4f

Correct answer is D

No explanation has been provided for this answer.

830.

How much heat is emitted when a body of mass 200g cools from 37oC to 31oC? (specific heat capacity of the body = 0.4Jg-1K-1,)

A.

4800J

B.

1200J

C.

480J

D.

202J

E.

80J

Correct answer is C

H = mC\(\theta\) = 200 x 0.4 x 6

= 480J