It is a common observation that rain clouds can be at about a kilometer altitude above the ground.
If the diameter of the rain drop is 4mm then Estimate the time required to flatten the drop.

It is a common observation that rain clouds can be at about a kilometer altitude above the ground. A typical rain drop is about 4 mm diameter. Momentum is mass xx speed in magnitude. Estimate its momentum when it hits the ground.

It is a common observation that rain clouds can be at about a kilometer altitude above the ground. Rate of change of momentum is force. Estimate how much force such a drop would exert on you.

It is a common observation that rain clouds can be at about a kilometer altitude above the ground. If a rain drop falls from such a height freely under gravity, what will be its speed? Also calculate in km/h. (G = 10 m//s^2) .

It is a common observation that rain clouds can be at about a kilometer altitude above the ground. Estimate the order of magnitude force on umbrella. Typical lateral separation between two rain drops is 5 cm. ( g = 10 m / s^2 and diameter of drop = 4mm)

Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity) :- the total mass of rain-bearing clouds over India during the Monsoon

A rain drop of radius 2 mm falls from a height of 500 nr above the ground. It falls with decreasing acceleration (due to viscous resistance of the air) until at half its original height, it attains its maximum (terminal) speed, and moves with uniform speed thereafter. What is the work done by the gravitational force on the drop in the first and second half of its journey ? What is the work done by the resistive force in the entire journey if its speed on reaching the ground is 10 m s^-1 ?

The normal activity of living carbon-containing matter is found to be about 15 decays per minute for every gram of carbon. This activity arises from the small proportion of radioactive "_6^14C present with the stable carbon isotope "_6^12C . When the organism is dead, its interaction with the atmosphere (which maintains the above equilibrium activity) ceases and its activity begins to drop. From the known half-life (5730 years) of "_6^14C , and the measured activity, the age of the specimen can be approximately estimated. This is the principle of "_6^14C dating used in archaeology. Suppose a specimen from Mohenjodaro gives an activity of 9 decays per minute per gram of carbon. Estimate the approximate age of the Indus-Valley civilisation.

The Millikan oil-drop experiment enabled the charge on the electron to be deterined. Two parallel metal plates P and Q are situated in a vaccum. The plates are horizontal and separated by a distance of 5.4 mm, as illustrated in fig. The lower plate P is earthed. The potential difference between the plates can be varied. An oil droplet of mass 7.7 xx 10^-15 kg is oserved to remain stationary between the plates , when palte Q is a t a potential of +850 suggest why plates p and Q must be parallel and horizontal and calcualte the charge with its gin, on the oil droplet.