Question

Q-17 Express the value of following quantities in their Si units
(a) power of electric lamo-2*10*9 erg s-1
(b) surface tension of water - 72 dyne cm-1​

Answer 1

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Answer 2

Answer:

(a) The SI unit of power of an electric lamp is 2 × 10² J/s.

(b) The SI unit of surface tension of water is 72 × 10⁻³ N/m OR 7.2 × 10⁻² N/m.

Explanation:

1N=10⁵ dyne

1J=10⁷ erg

1m=100cm

(a) P= 2 × 10⁹ × 10⁻⁷ J/s

      = 2 × 10² J/s

Hence, the SI unit of power of an electric lamp is 2 × 10² J/s.

(b) Surface Tension of water= 72 dyne cm⁻¹

                     n₁u₁ = n₂u₂

                  72 dyne/cm = n₂ (N/m)

                  n₂ = 72 × dyne/cm × m/N

                       =  72 × dyne/N × m/cm

                       = 72 ( 10⁻⁵ N / 1 N) × (100 cm/ 1cm)

                       = 72 × 10⁻⁵ × 100

                       = 72 × 10⁻³

Hence, the SI unit of surface tension of water is 72 × 10⁻³ N/m OR 7.2 × 10⁻² N/m.