WAEC Physics Past Questions & Answers - Page 223

1,111.

I Electrical potential,
II Torque,
III Kinetic Energy,
IV Momentum.

Which of the quantities listed are vectors?

A.

II and IV

B.

I and II

C.

I and III

D.

II and III

Correct answer is A

No explanation has been provided for this answer.

1,112.

A quantity which requires magnitude and direction to be specified is

A.

Temperature

B.

Distance

C.

Displacement

D.

Mass

Correct answer is C

Displacement is a vector quantity

1,113.

What is the least possible error encountered when taking measurement with a meter rule?

A.

0.1mm

B.

1.0mm

C.

0.5mm

D.

0.2mm

Correct answer is C

No explanation has been provided for this answer.

1,114.

An atom radiates 1.5 x \(10^{-19}\)J of energy when an electron jumps from one energy level to another. What is the wavelength of the emitted radiation? (Planck’s constant =6.6 x \(10^{-34}\)Js. Speed of light in air=3 x \(10^{8}ms^{-1}\)

A.

1.32 x \(10^{-6}\)m

B.

2.98 x \(10^{-6}\)m

C.

3.32 x \(10^{-6}\)m

D.

6.82 x \(10^{-6}\)m

E.

8.01 x \(10^{-6}\)m

Correct answer is A

\(E=\lambda v=\frac{hc}{\lambda}\Rightarrow\lambda=\frac{hc}{E}={6.6 \times10^{-34}\times3\times10^8}{1.5\times10^{-19}}\\=1.32\times10^{-6}\)

1,115.

In a nuclear reaction, the mass defect is 2 x \(10^{-6}\)g. Calculate the energy released given that the velocity of light is 3 x \(10^{8}ms^{-1}\)

A.

9 x \(10^{7}\)J

B.

1.8 x \(10^{8}\)J

C.

1.8 x \(10^{9}\)J

D.

9 x \(10^{-10}\)J

E.

3.6 x \(10^{11}\)J

Correct answer is B

E=\(mc^2 = 2\times10^{-6} \times10^{-3}\times(3\times10^{8})^2=1.8\times10^{8}\)