The energy supplied to Kolkata by the state electricity board during an average November week day was 40 GWh. If this energy could be obtained by the conservation of matter, how much mass would have to be annihilated?

Question

The energy supplied to Kolkata by the state electricity board during an average November week day was 40 GWh. If this energy could be obtained by the conservation of matter, how much mass would have to be annihilated? (A) 1.6 g (B) 2.2 g (C) 4.0 g (D) 1.6kg

Tardigrade Admin · Accepted Answer

E=40 G W h=(40 × 109 J / s ) (60 × 60 s )=1.44 × 1014 J But E=m c2 so, m=(E/c2)=(1.44 × 1014/(3 × 108)2) =1.6 × 103 kg i.e., m=1.6 g

Q. The energy supplied to Kolkata by the state electricity board during an average November week day was $40 G Wh$ . If this energy could be obtained by the conservation of matter, how much mass would have to be annihilated?

1.6 g

2.2 g

4.0 g

1.6kg

$E = 40 G Wh = (40 \times 1 0^{9} J / s)$
$(60 \times 60 s) = 1.44 \times 1 0^{14} J$
But $E = m c^{2}$
so, $m = \frac{E}{c ^{2}} = \frac{1.44 \times 1 0 ^{14}}{( 3 \times 1 0 ^{8} ) ^{2}}$
$= 1.6 \times 1 0^{3} k g$
i.e., $m = 1.6 g$

Q. The energy supplied to Kolkata by the state electricity board during an average November week day was 40GWh. If this energy could be obtained by the conservation of matter, how much mass would have to be annihilated?