WAEC Past Questions and Answers - Page 3485

17,421.

A radioactive substance of mass 768g has a half life of 3 years. After how many years does this substance leave only 6g undecayed?

A.

21

B.

18

C.

15

D.

12

Correct answer is A

\(768 \to 384 \to 192 \to 96 \to 48 \to 24 \to 12 \to 6\)

7 x 3 = 21yrs

17,422.

Cost-push inflation is likely to raise when

A.

There is an increase in government spending

B.

There is an increase in direct taxes

C.

Demand for higher wages is granted

D.

There is a decrease in banks lending

Correct answer is C

No explanation has been provided for this answer.

17,423.

A 500kV is applied across an X-ray tube. Calculate the maximum velocity of the electrons produced [Me = 9.1 x 10-31kg, e = 1.6 x 10-19C]

A.

4.2 x 108ms-1

B.

1.9 x 108ms-1

C.

4.2 x 105ms-1

D.

1.8 x 105ms-1

Correct answer is A

No explanation has been provided for this answer.

17,424.

The breaking up of an atomic nucleus into the fragment of nearly equal size is known as

A.

nuclear fusion

B.

nuclear fission

C.

thermonuclear reaction

D.

natural radioactivity

Correct answer is B

No explanation has been provided for this answer.