1998 - JAMB Physics Past Questions and Answers - page 5

The electrochemical equivalent of a metal is 1.3 x 10^-7kgC^-1. The mass of the metal which 2.0 x 10⁴C of electricity will deposit from a suitable electrolyte is

6.5 x 10^-2kg

2.6 x 10^-2kg

6.5 x 10^-3kg

2.6 x 10^-3kg

Answer & Comments

correct option: d

m = QZ

= 2 x 10⁴ x 1.3 x 10^-7

= 2.6 x 10^-3kg

Users' Answers & Comments

In a nuclear fusion experiment, the loss of mass amounts to 1.0 x 10^-6kg. The amount of energy obtained from the fusion is

3.0 x 10^-4J

3.0 x 10^-1J

9.0 x 10⁴J

9.0 x 10¹⁰J

Answer & Comments

correct option: d

Energy = mc²

= 1 x (3 x 10⁸)² x 10⁶

= 9 x 10¹⁰J

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In photoelectric effect, electrons will leave the metal surface when illuminated by light of appropriate frequency if the photon energy is

greater than the work function

less than the work function

equal to the work function

equal to the maximium kinetic energy of the electron

Answer & Comments

correct option: a

Users' Answers & Comments

A body on the ground is acted on by a force of 10N at a point P as shown in the fig above. What force is needed to stop the body from moving eastwards