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Class 10 Class 12

Work done in increasing the size of a soap bubble from a radius of 3 cm to 5 cm is nearly. (Surface tension of soap solution = 0.03 Nm-1)

• 4π mJ

• 0.2π mJ

• 2π mJ

• 0.4π mJ

D.

0.4π mJ

Work done = Change in surface energy
⇒ W = 2T x 4π (R22-R12)
= 2 x 0.03 x 4π [ (5)2-(3)2] x 10-4
= 0.4 π mJ

Work done = Change in surface energy
⇒ W = 2T x 4π (R22-R12)
= 2 x 0.03 x 4π [ (5)2-(3)2] x 10-4
= 0.4 π mJ

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Is work a scalar or a vector quantity?

Work is dot product of two vectors. i.e. .

And dot product is a scalar quantity. Therefore, work is a scalar quantity.
1450 Views

What is watt?

SI unit of power is Watt.
773 Views

Define watt.

Power is said to be one watt if one joule of work is done in one second.
860 Views

Define the unit joule.

Work done is said to be one joule if one newton of  force displaces the body through a distance of one meter in the direction of applied  force .
799 Views

What are different units of energy?

The different units of energy are :

(i) Joule
(ii) Erg
(iii) eV
(iv) KWh
(v) Calorie.

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