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# 6th Standard Science( Force and Motion) Important Short Notes for TNPSC / UPSC Exams: Download as PDF

Motion:When there is a change of position of an object with respect to time, then it is called motion.
Rest:When there is no change of position of an object with respect to time and if it remains stationary it is called rest.

How things move?
Application of forces result in motion of an object from rest. It may increase or decrease in speed,change in direction, and distortion of the shape.

Forces:Forces are push or pull by an animate or inanimate agency.

Types of Forces:
A.On the basis of contact
1. Contact Forces
2. Non-Contact Forces
Contact Forces:When the force is executed by touching the body such force is called Contact Force.
For example: Wind is making a flag flutter, a cart pulled by a bullock etc.
Non-Contact Forces:The force is applied without touching the object.Such forces are known as non-contact forces.For example: Magnetism, gravity etc.

B.On the basis of agencies
1. Animate Factors
2. Inanimate Factors
Animate Factors:It is a person or animal, that is an animate agency that does the pushing or pulling.
Inanimate Factors:The push or pull can be due to the inanimate agency like blowing wind and flowing water is the cause for a tall grass in the meadow dancing in the wind and a piece of wood is moving down a stream respectively.

What happens when we apply a force on an object?
When we apply a force on an object a force can -
1. Change the states of body from rest to motion or motion to rest.
2. Either change the speed or direction or both of the body.
3. Change the shape of the body.

Vibrations: Fast oscillations are referred to as vibrations.

Speed : The distance travelled by an object in unit time is called average speed of the object.
• If an object travelled a distance (d) in time (t) then its Average speed (s)  = distance travelled / time taken = d/t.
• The SI unit of average speed is metre/second.
Classification Of Motion :We can classify the motion on the following basis -
1) Based on path
2) Based on duration
3) Based on speed

1) Based on path :You can classify the motion according to the path taken by the object.

a. Linear motion - moving in a straight line, like a person walking on a straight path, free fall.

b. Curvilinear motion - moving ahead but changing direction, like a throwing ball.

c. Circular motion - moving in a circle, swirling stone tied to the rope.

d. Rotatory motion - The movement of a body about its own axis, like a rotating top.

e. Oscillatory motion - coming back to the same position after a fixed time interval, like a pendulum.

f. Zigzag (irregular) motion - like the motion of a bee or people walking in a crowded street.

2) Based on duration:You can classify the motion according to the duration taken by the object.
a. Periodic motion: Motion repeated in equal intervals of time is called as periodic motion.
For example:Revolution of the moon around the earth is periodic motion.
b. Non-Periodic motion: Motion is not in uniform interval. Such Motions are called non-periodic motion.
For example: sabing swing in wind.

3) Based on speed:You can classify the motion according to the speed of an object.
a.Uniform motion : If an object covers uniform distances in uniform intervals then the motion of the object is called Uniform Motion.
b.Non-Uniform motion:  If an object covers uniform distances in non-uniform intervals then the motion of the object is called Non-Uniform Motion.

Science Today - Robot
• The term comes from a czech word, ‘robota’ meaning ‘forced labour’.
• Robotics is the science and study of robots.
• Electronic sensors are a robot’s eyes and ears.
• Twin video cameras give the robot a 3-D view of the world.
• Microphones detect sounds.
• Pressure sensors give the robot a sense of touch, to judge how hard to grip an egg.
• Heavy luggage built-in computers send and receive information with radio waves.
• Artificial intelligence attempts to create computer programs that think like human brains.
• Nano-robots or nanobots are robots scaled down to microscopic size in order to put them into very small spaces to perform a function.