There are two separate coils in a heater . If one col is used then it takes 20 minutes to boil a given amount of water completely. But when its other coil is used then it takes 5 minutes to boil the same amount of water. Calculate the time taken to boil the same amount of water using the same source when the two coils are connected (1) in series and (2) in parallel.

Take two identical trays and fill them with soil. Plant mustard or green gram or paddy in one of the trays and water both the trays regularly for a few days, till the first tray is covered by plant growth. Now, tilt both the trays and fix them in that position. Make sure that both the trays are tilted at the same angle. Pour equal amount of water gently on both trays such that the water flows out of the trays. Now pour equal amounts of water on both the trays from a height. Pour three or four the amount that you poured earlier. Study the amount of soil that is carried out of the trays now. Is the amount the same in both the trays ?

An open metal bucket is in the shape of a frustum of a conce. Mounted on a hollow cylinderical base made of the same metallic sheet (see the given figure) the diameters of the two circular ends of the bucket are 45 cm and 25 cn. The vertical height of the bucket is 40 cm and that of the cylinderical base is 6 cm. find the area of the metallic sheet used to make the bucket, hwere we do not tak einto account the handle of the bucket. also, find the volu8me of water the bucket can hold (Take pi=(22)/(7))

A solid sphere rolls down two different inclined planes of the same heights but different angles of inclination. (a) Will it reach the bottom with the same speed in each case? (b) Will it take longer to roll down one plane than the other? (c) If so, which one and why?

A solid sphere rolls down two different inclined planes of the same heights but different angles of inclination. (a) Will it reach the bottom with the same speed in each case? (b) Will it take longer to roll down one plane than the other? (c ) If so, which one and why?

There are two cylinder shaped wooden bullets, each having mass M, in a vertical wall sewage, which contains water in it. The two bullets have same size and same material , they touch each other and walls of sewage. One of them is totally under water, where the other one is immersed only half into water. Friction is negligible if density of wood is given by (3)/(x)p_(omega) (p_(omega) "is density of water") then find x

Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at equator. Will the friend agree with the weight of gold bought? If not, why? [Hint : The value of g is greater at the poles than at the equator.]

An ideal gas is allowed to expand against a constant pressure of 2 bar from 10 L to 50 L in one step. Calculate the amount of work done by the gas. If the same expansion were carried out reversibly, will the work done be higher or lower than the earlier case ? (Given that 1 L bar = 100 J)

The figure shows two thin rods , one made of aluminium [alpha = 23 xx 10^(-6) (C^(@))^(-1)] and the other of steel [alpha = 12 xx 10^(-6) (C^(@))^(-1)] . Each rod has the same length and the same initial temperature . They are attached at one end to two separate immovable walls. Temperature of both the rods is increased by the same amount , until the gap between the rods vanishes . Where do the rods meet the gap vanishes?

Two small boats are 10m apart on a lake. Each pops up and down with a period of 4.0 seconds due to wave motion on the surface of water. When one boat is at its highest point, the other boat is its lowest point. Both boats are always within a single cycle of the waves. The speed of the waves is: