A glass plate of length 10 cm, breadth 4 cm and thickness 0.4 cm weighs 40 g in air. If it is held vertically with long side horizontal and the plate half immersed in water, what will be its apparent weight? Surface tension of water ` = 70 dyne cm^-1`.

If surface tension of water is 70 dyn cm^-1 , what is its value in S.I.?

A glass (mu=1.5) convex lens of focl length 40 cm is placed in water (mu=1.3) .What will be its new focal length?

A bar magnet of length 8 cm and having a pole strengh of 1.0 A m is placed vertically on a horizontal table with its south pole on the table. A neutral point is found on the table at a distance of 6.0 cm north of the magnet. Calculate the earth's horizontal magnetic field.

A convex lens of refractive index 1.5 has a focal length of 18 cm in air.Calculate the change in focal length,when it is immersed in water of refractive index 4//3 .

A wire is in the shape of a rectangle. Its length is 40 cm and breadth is 22 cm. If the same wire is rebent in the shape of a square, what will be the measure of each side. Also find which shape encloses more area?