# General Awareness

General Awareness -Physics -Force

1-Force is a physical quantity which changes or tends to change the position of a body. It is a push or pull.

2-If there is a physical contact between the two bodies which are interacting then the force applied is called Contact force.Muscular force, force of friction ,normal force,tension are examples of contact force.

3-The force which we exerts by using our body muscles is known as muscular force.

4-Force of friction means friction is the force that opposes relative motion of surfaces in contact.

5-The force which is acting opposite to gravitational force and perpendicular to surface of contact is called normal force.

6-When you try to stretch a rope or a string the tightness of rope or string is called tension.

7-Forces that change the motion of an object without actual touching is called non-contact force.This is also called force acting at a distance.

8-Magnetic force,electrostatic force, force and gravitational forces are examples of non-contact forces.

9-The force exerted by a magnet on another magnet is called magnetic force.

10-The attractive force between any two massive objects in the universe is called gravitational force.

11-The force exerted by a charged body on other charged or uncharged body is known as electrostatic force.

12-Force has magnitude as well as direction and hence force is a vector quantity.

13-The strength of the force is usually expressed by its magnitude.

14-If the body does not move even after two equal forces acting on it in opposite direction then it is said to be in equilibrium.

15-The algebraic sum of all the forces acting on a body is called net force.It is denoted by F net.

16-Net force on an object is zero if two forces acting on it in opposite direction are equal.

17-The force acting on a unit area of a surface is called pressure.

18-The amount of force which is measured is known as magnitude of force.

19-If the body is in motion, then it is said to be in state of motion.

20-The diagram showing all the forces acting on an object at a particular instant is called free body diagram(FBD).

21-Examples for force at a distance

a- When a needle is placed near to a magnet ,it gets attracted.

b- The gravitational force between the earth and the moon.

22-What are the theoretical and gravitational units of force ?
C.G.S                 MKS  and  SI

Theoretical Units          Dynes                 Newtons
Gravitational Units      Gram Wt.             Kg Wt.

23- I Kg Wt =  9.8 newtons   and  I gm Wt = 980 dynes .

24- Pressure is Scalar quantity.

25-The escape velocity of the earth is 11.2 kms where as air molecules in atmosphere have less than that.

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