Scalar and vector quantities

A study of motion will involve the introduction of a variety of quantities, which are used to describe the physical world. Examples of such quantities are distance, displacement, speed, velocity, acceleration, mass, momentum, energy, work, power etc. All these quantities can be divided into two categories – scalars and vectors. The scalar quantities have magnitude only. It is denoted by a number and unit. Examples : length, mass, time, speed, work, energy,temperature etc. Scalars of the same kind can be added, subtracted, multiplied or divided by ordinary laws. The vector quantities have both magnitude and direction. Examples: displacement, velocity, acceleration, force, weight, momentum, etc.

Comments

Post a Comment

Popular posts from this blog

Acceleration due to gravity

Galileo was the first to make a systematic study of the motion of a body under the gravity of the Earth. He dropped various objects from the leaning tower of Pisa and made analysis of their motion under gravity. He came to the conclusion that “in the absence of air, all bodies will fall at the same rate”. It is the air resistance that slows down a piece of paper or a parachute falling under gravity. If a heavy stone and a parachute are dropped where there is no air, both will fall together at the same rate. Experiments showed that the velocity of a freely falling body undergravity increases at a constant rate. (i.e) with a constant acceleration. The acceleration produced in a body on account of the force of gravity is called acceleration due to gravity. It is denoted by g. At a given place, the value of g is the same for all bodies irrespective of their masses. It differs from place to place on the surface of the Earth. It also varies with altitude and depth. The value of g at sea−lev...
Read more

Weightlessness

Television pictures and photographs show astronauts and objects floating in satellites orbiting the Earth. This apparent weightlessness is sometimes explained wrongly as zero–gravity condition. Then, what should be the reason? Consider the astronaut standing on the ground. He exerts a force (his weight) on the ground. At the same time, the ground exerts an equal and opposite force of reaction on the astronaut. Due to this force of reaction, he has a feeling of weight. When the astronaut is in an orbiting satellite, both the satellite and astronaut have the same acceleration towards the centre of the Earth. Hence, the astronaut does not exert any force on the floor of the satellite. So, the floor of the satellite also does not exert any force of reaction on the astronaut. As there is no reaction, the astronaut has a feeling of weightlessness.
Read more

Uses of satellites

(i) Satellite communication Communication satellites are used to send radio, television and telephone signals over long distances. These satellites are fitted with devices which can receive signals from an Earth – station and transmit them in different directions. (ii) Weather monitoring Weather satellites are used to photograph clouds from space and measure the amount of heat reradiated from the Earth. With this information scientists can make better forecasts about weather. Youmight have seen the aerial picture of our country taken by the satellites, which is shown daily in the news bulletin on the television and in the news papers. (iii) Remote sensing Collecting of information about an object without physical contact with the object is known as remote sensing. Data collected by the remote sensing satellities can be used in agriculture, forestry, drought assessment, estimation of crop yields, detection of potential fishing zones, mapping and surveying. (iv) Navigat...
Read more