A 0.5 kg block moving at a speed of 12 ms$$-$$1 compresses a spring through a distance 30 cm when its speed is halved. The spring constant of the spring will be _______________ Nm$$-$$1.
The velocity of upper layer of water in a river is 36 kmh$$-$$1. Shearing stress between horizontal layers of water is 10$$-$$3 Nm$$-$$2. Depth of the river is __________ m. (Co-efficient of viscosity of water is 10$$-$$2 Pa.s)
A steam engine intakes 50 g of steam at 100$$^\circ$$C per minute and cools it down to 20$$^\circ$$C. If latent heat of vaporization of steam is 540 cal g$$-$$1, then the heat rejected by the steam engine per minute is __________ $$\times$$ 103 cal.
(Given : specific heat capacity of water : 1 cal g$$-$$1 $$^\circ$$C$$-$$1)
The first overtone frequency of an open organ pipe is equal to the fundamental frequency of a closed organ pipe. If the length of the closed organ pipe is 20 cm. The length of the open organ pipe is _____________ cm.