Category Physics

            The waves are higher near beaches than in interior parts of the sea mainly because of the shallowness of the sea near beaches. The shape of the coast and surface features of the sea bottom near the coast also decide the height of the waves. In deep seas, the water in a wave moves in large vertical circles, without actually moving forward. Near the beaches such circulation is modified by the closeness of the bottom. This leads to increase in the height of the waves. Speed and direction of the wind, and the distance over which the wind is blowing are other factors that can further affect the height of waves. A                                                                                         strong wind can create huge waves even in mid sea.

            Rivers usually meander when they flow over the plains. On the plains, the gradient is usually low and river has no preferred direction of flow. Its course is usually determined by local irregularities in the terrain and soil condition. In such a situation when the river bends in one direction, it tends to scoop out its outer bank and deposit silt on the inner bend. After scouring one bank the water is deflected towards the opposite bank which now starts getting eroded. The process continues with the river changing direction over short distances, giving rise to the familiar meanders.

            Clouds are large masses of fine water droplets or ice particles formed by condensing water vapour. In spite of their great masses, clouds float in the sky because they are held up by the up drift caused by hot air rising from the ground below. Within the clouds themselves strong currents of upward rising air keep the droplets or ice crystals in constant motion which not only helps them keep afloat but also leads to the rapid changes in shapes of clouds.

            Ice skating is an act of gliding over the smooth surface of hard ice on ice skates – boots with attached metal blades. It is easy t skate on hard and smooth surface of ice because of the absence of frictional force between ice and the skating blade. Another reason is that ice melts under the pressure of the sharp blades of the skate and water thus formed acts as a lubricant which helps in skating. It is not possible to skate on snow or sand because the surface is not hard.

For any living being to get electrocuted, a current of sufficient voltage has to pass through its body, i.e. there should be completion of the electric circuit. Birds perching on live electric transmission lines are not killed because they are in contact with only on wire and no current passes through them. But if the bird sitting on a live-wire simultaneously comes in contact with the ground or touches another live-wire, the electric circuit would be complete and the bird will be killed by the current flowing through it. Similarly a person hanging on to a single live-wire will not be electrocuted unless he touches the ground or the earth wire.

Earth rotates from west to east causing the Sun, the Moon, stars andother planets rise from

east and set in the west. On the surface of the eartheach point is moving eastward with

respect to an astronaut in space.

Thus if a rocket is launched at a small angle eastward vertically the speed of earth gets added to

the rocket’s speed. This reduces the amount of fuelrequired. If the rocket is inclined along any

other direction, the speed of the earth gets subtracted from the speed of rocket and will

necessitate burning of more fuel.

In addition, in case of any failure during launch the rocket will fall back to the earth.

Hence if it is launched from the east coast, the rocket will fall into the sea only. If it is launched from the west coast, in case of failure, the rocket will fall on the land endangering human habitats. Thus choosing eastward inclination is scientific but choice of eastern coast concerns safety.

In normal telephone exchange systems, a pair of wires extends each telephone instrument to the telephone exchange.

Normally, copper conductors are used to give loop to indicate the exchange that the 

Continue reading “How does a cell phone work?”

Down to milligrams one can use well-designed physical balances-indeed one can even o below one milligram if proper isolation from vibrations and other disturbances is ensured. But for going lower one needs to use other methods. We have to remember that our objective is to measure the mass, which is the quantity of material and not the amount of gravitational force. Mass is a measure of inertia.

Continue reading “How are minute quantities (like milligrams, micrograms, or nanograms) weighed?”