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MOTION

MOTION. What is motion ? What are the different types of motion? What is the physics relating to motion called? ok! we have answers to all these questions. 1. what is motion?.

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MOTION

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  1. MOTION What is motion ? What are the different types of motion? What is the physics relating to motion called? ok! we have answers to all these questions.

  2. 1. what is motion? when a body is continuously changing its position with respect to the surroundings , then we say that the body is in motion.

  3. EXAMPLE 1.When an athlete is running on the ground then he is continuously changing his position with respect to the audience who are sitting at rest. 2.We are continuously changing our position since morning till night with respect to earth which is at rest. 3.The earth is continuously changing position with respect to sun which is at rest.

  4. object in motion? • If you are standing in one place, and your friend walks by you, are you moving relative to your friend? • Is your friend moving relative to you? • Is either of you moving relative to the earth?

  5. Answer: • You are moving relative to your friend, and your friend is moving relative to you! • You (the Joker) are not moving relative to the earth, but your friend is. You are both moving relative to the sun! Who is moving relative to the computer screen?

  6. 2.What are the different types of motion? Linear motion : when a body moves either in a straight line or along a curved path, then we say that it is executing linear motion. 1. when a body moves in a straight line then the linear motion is called rectilinear motion. eg ., an athlete running a 100 meter race along a straight track is said to be a linear motion or rectilinear motion. 2.when a body moves along a curved path then the linear motion is called curvilinear motion. eg., a planet revolving around its parent star

  7. Other types of motion are : Rotatory motion : A body is said to be in rotatory motion when it stays at one place and turns round and round about an axis. example :a rotating fan, a spinning top, the earth. Oscillatory motion : a body is said to be in oscillatory motion when it swings to and fro about a mean position. example : the pendulum of a clock, the swing etc.,

  8. Vibratory motion When a certain part of a body always remains fixed and the rest of the body moves to-and-fro in a definite style, then its motion is called vibratory motion. Periodic motion A motion which repeats itself at regular interval of time is called periodic motion.

  9. Multiple motion When an object possesses two or more types of motions at the same time, then such a motion is called multiple motion. examples: When a spin bowler delivers a ball, the ball has a motion of spin(rotatory motion)while it moves toward the batsman(translatory motion).

  10. SIMPLE PENDULUM AND RESTORING FORCE

  11. PERIODIC MOTION • The motion which repeats itself after fixed time intervals is called periodic motion The best example of periodic motion are the pendulum clocks.

  12. A SIMPLE PENDULUM • A string with a mass at the end which is free to swing is called a pendulum.

  13. TO AND FRO MOTION • The ball moves to and fro. It rises to extreme positions on both sides and reverses its motion • Oscillations gradually die down

  14. LENGTH OF THE PENDULUM • The length of the string from the point of suspension to the mass is called the length of the pendulum. • It is denoted by L

  15. MEAN POSITION OF THE PENDULUM • The central position of the pendulum (the starting position) is called the mean position of the pendulum. • It is labeled here as B.

  16. EXTREME POSITIONS OF THE PENDULUM • A and C are the extreme positions of the pendulum.

  17. OSCILLATION • The motion of the mass from its extreme position A to C and back to A is called an oscillation.

  18. TIME TAKEN FOR ONE OSCILLATION • The time taken for one oscillation is very short and therefore, difficult to measure accurately. • To find the time taken, we find the time taken for large number say 20 oscillations. This time divided by 20 will give us time taken for one oscillation.

  19. PERIODIC TIME OF THE SIMPLE PENDULUM • The time taken to complete one oscillation is called the periodic time of the simple pendulum. • It is sometimes also called its period and is denoted by T.

  20. RELATIONSHIP BETWEEN T AND L • The equation is The Period of the pendulum T is related to the length L by the relation

  21. Factor affecting Time period of simple of pendulum • Time period of simple pendulum depend on length and acceleration due to gravity (g) • Time period of simple pendulum does not depend on mass of bob and material of bob

  22. SCALARS AND VECTORS The motion of objects can be described by words - words such as distance, displacement, speed, velocity, and acceleration. These mathematical quantities which are used to describe the motion of objects can be divided into two categories. The quantity is either a vector or a scalar. These two categories can be distinguished from one another by their distinct definitions: Scalars are quantities which are fully described by a magnitude alone. Eg: distance , mass ,time ,volume etc Vectors are quantities which are fully described by both a magnitude and a direction. Eg :displacement , velocity , force ,acceleration etc.,

  23. DISTANCE Distance is the actual path covered by a body, irrespective of its direction. Hence, it is scalar quantity. Displacement Displacement is shortest distance travelled by a body from its initial position to its final position in particular direction Hence , it is a vector quantity. It indicates the change in position of a body. Therefore, has both length and direction

  24. Here’s a problem (or two)….. If the earth spins on its axis at 1100 miles/hour, what is the speed of the Earth's rotation in feet per second? The earth travels at 68,000 miles/hour as it moves around the sun. How many miles does the earth travel in one trip around the sun?

  25. Speed Speed is the distance traveled in a given amount of time Speed=distance time The units for speed: meters/second (m/sec) kilometers/hour (km/hr) Speed that does not change is constant speed

  26. Speed • Speed = Distance time s = d t Example: A car travels 450km in 5 hours. What is the speed of the car?

  27. Answer: • Speed = distance time • Speed = 450 Km 5 hours • Speed = 90km hr

  28. More practice • 1. How far can a plane travel if it flies 800km/hr for 9 hours? • 2. How long does it take a ship to go 500 km if it travels at a speed of 50km/hr?

  29. 1. Answer Then: d = s t 800km 9hr = 7200km hr

  30. 2.Answer And then: since s = d t t = d s 500km 1hr = 10hrs 50km

  31. Velocity velocity is the rate of change of the position of an object, equivalent to a specification of its speed and direction of motion. Speed describes only how fast an object is moving, whereas velocity gives both how fast and in what direction the object is moving. If a car is said to travel at 60 km/h, its speed has been specified. However, if the car is said to move at 60 km/h to the north, its velocity has now been specified. To have a constant velocity, an object must have a constant speed in a constant direction.

  32. Velocity • Speed in a given direction. • What is the velocity of a boat that travels from St. Peter to Mankato (10 miles) in 15 minutes?

  33. Answer • Speed = distance = 10miles time 15min • Speed = 0.6666667 mil = 0.7 mil min min

  34. Change your answer to mi/hr! • 0.67mi 60min = min hr • 40 mi hr

  35. Velocity can be classified as uniform and variable velocity Uniform velocity :- If a body travels with a uniform speed in a constant direction, then the body is said to have uniform or constant velocity Variable velocity :- we normally come across variable velocities of moving bodies, Which means speed or direction or both speed and direction of moving bodies change constantly

  36. Speedvelocity • It is the rate of change of distance • It is a scalar quantity • speed of moving body cannot be zero • It is the rate of change of displacement • It is a vector quantity • The velocity of a moving body become zero if it return to its initial position.

  37. Acceleration The change in velocity is Acceleration Acceleration is measured in m/sec2 Formula is: final velocity – original velocity time taken

  38. Uniform and nonuniform acceleration Acceleration can be uniform or nonuniform. Nonuniform acceleration requires a change in acceleration. For example, when you’re driving, you encounter stop signs or stop lights often, and when you decelerate to a stop and then accelerate again, you take part in nonuniform acceleration. Other accelerations are very uniform (in other words, unchanging), such as the acceleration due to gravity on the surface of the earth. This acceleration is 9.8 meters per second2 downward, toward the center of the earth, and it doesn’t change (if it did, plenty of people would be pretty startled).

  39. ACCELERATION • Problem: A car is moving in a straight line it speed up from 65km/hr to 74km/hr, in .17hrs What is the car’s acceleration. • Acceleration = Vf –Vi 1 t 74kmf – 65kmi 1 = hr hr 0 .17hr 53 km/hr2

  40. ACCELERATION!!! • Problem: Suppose a car moving in a straight line steadily increases its speed each second. First from 35 to 40 km/hr, then from 45 to 50 km/hr. What is its acceleration?

  41. Answer • 15km 1h 1min 1 = .001 km • hr 60 min 60 sec 3 sec2

  42. DEACCELERATION • Deceleration ( “negative” acceleration): • A term commonly used to mean a decrease in speed. • Acceleration in a direction opposite to the direction of travel. • Deceleration is negative acceleration and has a negative value to indicate direction.

  43. Relation between uniform acceleration and time • Suppose body start with initial velocity of u m/s , Now body go on increasing its velocity by an amount a uniformly , let its final velocity be v m/s after a time of t sec a = final velocity – original velocity time take = (v-u)/t Or v= u + at This is called equation of motion

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