Motion

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1. Motion

2. Motion The change of position of an object with respect to time.

3. Motion used in Physical Quantities Motion is typically described in terms of displacement, distance (scalar), velocity, acceleration , time and speed.

4. Motion in One Dimension When a body moves along a straight line path It is also called as Rectilinear Motion Ex: An ant moving in straight line, running athlete

5. Motion In Two Dimensional If a body moves along a Curved Path. It is also called as Curvilinear Motion Ex: throwing paper airplanes, a body moving in a plane

6. Motion In Three Dimensional The position of body change => If a body moves in space; It is also called as Random Motion Ex: motion of a flying bird, kite in the sky, molecule, etc…,

7. Motion in one Dimension The important parameters required to study the motion along a straight line are position, displacement, velocity, acceleration. The motion of a particle can be described if its position is known continuously with respect to time.

8. Distance The Length of the path traversed by a body is called travelled by it. The path may not be straight.

9. Displacement The Shortest distance from the initial to the final position of the body is called the magnitude of displacement.

10. Distance Displacement 1 .”How much ground an object has covered” during its motion 1. ”Howfar out of place an object is” ; It is the objects overall change in position. 2.It is Scalar Quantity i.e it only has the magnitude. 2. 2.It is Vector Quantity i.e it has both the magnitude and direction. 3.It depends on path 3. It does not depend on the path 4.It is always positive 4. It can be Positive or Negative depending on direction. 5. The length of the path between two objects . 5. The total length of the path is the distance travelled by the particle and t he Shortest distance between the initial and final position of the particle.

11. Vector The Vector quantities have both magnitude and direction . Ex : acceleration , force , displacement , velocity, weight, momentum, etc…

12. Scalar The Scalar quantities have magnitude only It is denoted by a number and unit . Ex: pressure, length, mass, time, speed, work, energy, temperature, etc…

13. Speed The Speed Of a body is the rate of change of distance with time. It is scalar quantity. It is represented by the letter u & v. Speed = Distance / Time The S.I unit of Speed is m/s

14. Velocity The Velocity of a body is the distance travelled per second by the body in a specific direction. It is a vector quantity. Velocity = displacement / time The S.I unit of Velocity is m / s

15. Speed Velocity The distance travelled per second by a moving object is called speed. The distance travelled per second by a moving object in a particular direction is called velocity. Scalar Quantity Vector Quantity The Speed is always positive. The Velocity can be positive or negative depending upon the direction of motion.

16. Acceleration The rate of change of change of velocity with time. Acceleration = Velocity / Time It is Vector quantity; Represented by the symbol a

17. Retardation If the velocity decreases with time , the acceleration is negative . The negative acceleration is called retardation or deceleration.

18. Random Motion: The irregular motion of small particles suspended in a liquid or a gas Ex: a fish swimming in water

19. Rotational Motion : A  rotation  is a circular movement of an object around a center (or point) of rotation Ex: as the wheel of a bicycle, wind mill

20. Rectilinear Motion : Ex: when a body moves in a straight line path Curvilinear Motion: Ex: throwing paper airplanes Circular Motion: Ex: the orbits of planets

21. Uniform Motion The object covers equal distances in equal intervals of time is called uniform motion.

22. Non - Uniform Motion The object covers unequal distances in equal intervals of time is called uniform motion. Ex : when a car is moving in a traffic

23. Equation of Motion When an object moves along a straight li ne with uniform acceleration , it is possible to relate its velocity, acceleration during motion and the distance covered by it in a certain time interval by a set of equations known as the Equations of motion .

24. Equation for Velocity – Time Relation Acceleration = change in velocity / time a = v-u / t at= v-u v= u + at

25. Equation for Position – Time Relation Distance = Average Velocity / time S = u+v / 2 X t = u+( u+at )/2 X t = (2u+at/2) X t = ut + ½ at^2

26. Equation for Position - Velocity Relation Distance = Average Velocity X time s = u+v / 2 X t s = u+v / 2 X v-u / a = v^ 2 –u^ 2 / 2a 2as = v^ 2 – u^ 2 v^ 2 = u^ 2 + 2as

27. PROBLEMS 1.A train moving with uniform speed covers a distance of 120m in 2 s. Calculate i ) the speed of the train ii) the time it will take to cover 240 m. 2. Find the distance travelled by a body in 5 mins if it travels with a uniform speed of 20 m/s. 3. Express the speed 36 km / h in m / s 4. The velocity of an object increases at a constant rate from 20 m/s to 50 m/s in 10 s. Find the acceleration. 5. A pebble thrown vertically upwards with an initial velocity 50 m/s comes to a stop in 5s. Find the retardation .

28. Uniform Circular Motion : When an object moves in a circular path with uniform speed, its motion is called Uniform Circular Motion.

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