A wind with speed 40 m/s blows parallel to the roof of a house. The area of the roof is 250 m². Assuming that the pressure inside the house is atmospheric pressure, the force exerted by the wind on the roof and the direction of the force will be $$({\rho _{air}} = 1.2kg/{m^3})$$

Steam at 100^oC is passed into 20 g of water at 10^oC. When water acquires a temperature of 80^oC, the mass of water present will be
[Take specific heat of water = 1 cal g^{$$-$$1 o}C^$$-$$1 and latent heat of steam = 540 cal g^$$-$$1]

A certain number of spherical drops of a liquid of radius r coalesce to form a single drop of radius R and volume V. If T is the surface tension of the liquid, then

Copper of fixed volume V is drawn into wire of length $$l$$. When this wire is subjected to a constant force F, the extension produced in the wire is $$\Delta $$$$l$$. Which of the following graphs is a straight line ?