RRB NTPC Exam 2016 will test you on Gravity– the fundamental force that attracts objects together. Learn about Gravity and Take the Quiz that follows.

## RRB NTPC Exam 2016 #Daily Infographic on General Science (Physics)

### Gravity Explained

Gravity represents the attraction between objects. All objects with mass are affected by gravity. Gravity acts like a magnet — pulling objects together.

The Earth has gravity. Gravity holds everything close to this planet. Trees, water, animals, buildings, and the air we breathe are all held here by gravity.

All of the planets, their moons, and the stars in the universe have gravity.

Even our own bodies have gravity. The Earth’s gravity is far stronger than our own so we don’t notice the gravity our bodies possess.

### Black Holes

Imagine gravity pulling on everything and not letting it escape — not even light! This is the essence of a black hole. The gravity in black holes pulls everything back in toward its center which may be as small as a single atom. This makes a black hole invisible because even light is unable to break away from its effects. Scientists believe there may be millions of black holes in the Milky Way Galaxy.

### Astronauts in Space

How do astronauts float in space if the pull of gravity is so strong? Astronauts don’t actually float. They are being pulled by the Earth’s gravity just the same as the rest of us.

But they are also orbiting the Earth, or moving sideways. This is known as centrifugal force. This sideways movement actually is pulling them away from the Earth at the same time that the Earth is pulling them down, so it appears as if they are floating.

### Escape Velocity

It is the minimum speed an object must attain in order to leave the gravitational pull of another body. In most cases this is referring to the earth. That was the first body of mass that scientists could learn how to leave. Later on it was the moon. Perhaps some day we will learn to leave other bodies in our solar system. For earth, escape velocity is about 7 miles per second or 25,000 miles per hour.

### Important Formula

F = G M m/r2

Here F = Force of Gravity

G = Gravitational Constant (6.67408 × 10-11 m3 kg-1 s-2)

M = Mass of one object

m = Mass of other object

r = Distance between two objects

### TAKE THE QUIZ ON GRAVITY

#### How to Prepare General Science Section for RRB NTPC Exam

References: www.idahoptv.org

1. See Weight = Mass X Gravity

Mass of the man on the moon = 70 Kgs
Acceleration due to gravity on the moon = 1.62 m/s2 (Memorize this value)

Hence Weight = 70 x 1.62

= 113.4 N (newton)

The mass of any body remains constant in the universe. So the mass of this man will be same on the Earth as well as the Moon i.e 70 Kgs.