A village has a population of 4000, requires 150 litres water per head per day. It has a tank measuring 20 m, 15 m, 6 m. How many days for the water is sufficient enough once the tank is made full ?

A photodiode sensor is used to measure the output of a 300 W lamp kept 10 m away. The sensor has an opening of 2 cm in diameter. How many photons enter the sensor if the wavelength of the light is 660 nm and the exposure time is 100 ms. (Assume that all the energy of the lamp is given off as light and h = 6.6 xx 10^(-34) Js )

Find out the usage of water in litres per day in your home ? Do you actually require that much water and how much water is enough in accordance with National standards ?

An overhead water tanker is in the shape of a cylinder has capacity of 61.6 cu.mts. The diameter of the tank is 5.6 m. Find the height of the tank.

On a particular day, the rainfall recorded in a terrace of dimensions 6 m and 5 m is 15 cm. The quantity of water collected in terrace is

Urine normally has a pH of 6.0 . A patient eliminates 1.3 litres of uring per day . How many moles of H^(+) ions does he eliminate in a day ?

Parvali house has a water tank in the shape of a cylinder on the roof. This is filled by pumping water from a sump (an underground tank) which is in the shape of a cuboid. The sump has dimensions 1.57 m times 1.44 m times 9.5 cm. The water tank has radius 60 cm. and height 95 cm. Find the height of the water left in the sump after the water tank has been completely filled with water from the sump which had been full of water. Compare the capacity of the tank with that of the sump. ( pi =3.14)

The amount of oxygen used by the suitable microorganisms present in water during five days at 20^(@)C is called as BOD. For pure water BOD is about 1 ppm fairly pure water 3 ppm and doubtful purity 5 ppm the municipal sewage has BOD values 100-4000 ppm. BOD= Number of moles of O_2 required / Number of liters of water sample The BOD values of three water sample x,y and z are 5 mg/litre, 16 mg/Litre and 400 mg/Litre respectively the more polluted sample of water is