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KINEMATICS

DESCRIBING MOTION. Physics progresses not by revolutions, which do away with all that went before, but rather by evolutions, which exploit the best about what is already understood. Newton's laws will continue to be as true today, no matter what we discover at the frontiers of science. Lawr

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KINEMATICS

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    1. KINEMATICS 4TH ESO Chemistry and Physics IES AMES

    2. DESCRIBING MOTION Physics progresses not by revolutions, which do away with all that went before, but rather by evolutions, which exploit the best about what is already understood. Newton's laws will continue to be as true today, no matter what we discover at the frontiers of science. Lawrence M. Krauss The Physics of Startrek

    3. DESCRIBING MOTION In the day we sweat it out in the streets of a runaway american dream At night we ride through mansions of glory in suicide machines Sprung from cages out on highway 9, Chrome wheeled, fuel injected and steppin out over the line Baby this town rips the bones from your back Its a death trap, its a suicide rap We gotta get out while were young `cause tramps like us, baby we were born to run Wendy let me in I wanna be your friend I want to guard your dreams and visions Just wrap your legs round these velvet rims And strap your hands across my engines Together we could break this trap Well run till we drop, baby well never go back Will you walk with me out on the wire `cause baby Im just a scared and lonely rider But I gotta find out how it feels I want to know if love is wild, girl I want to know if love is real

    4. DESCRIBING MOTION Kinematics is the science of describing the motion of objects using words, diagrams, numbers, graphs, and equations. The goal of any study of kinematics is to develop sophisticated mental models which serve to describe (and ultimately, explain) the motion of real-world objects. In this chapter you will learn: How to describe motion in terms of distance, displacement, velocity, acceleration and time. How to use equations to link these quantities How to draw and interpret graphs representing motion

    5. DESCRIBING MOTION

    6. DESCRIBING MOTION Physics is a mathematical science - that is, the underlying concepts and principles have a mathematical basis. 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 number alone. Vectors are quantities which are fully described by both a number and a direction.

    7. DESCRIBING MOTION In science we define motion as the change in position with time. How fast an object changes position or the rate that an object’s position changes with time is called the speed. If we know both the direction in which an object moves and its speed, then the combined direction and speed are called the velocity of an object. When either the speed or the velocity of an object is zero, then there is no motion.

    8. DESCRIBING MOTION Distance and displacement are both ways of measuring how far an object has moved. Distance is a scalar quantity which refers to "how much ground an object has covered" during its motion. Displacement is a vector quantity which refers to "how far out of place an object is"; it is the object's change in position. Displacement is the distance moved in a particular direction.

    9. DESCRIBING MOTION

    10. DESCRIBING MOTION Speed and velocity are both ways of measuring how fast an object has moved. Speed is a scalar quantity which refers to “the rate of change of distance”. average speed= distance travelled (m)/ time taken (s) Velocity is a vector quantity which refers to “the rate of change of displacement”. average velocity= total displacement (m)/ time taken (s) Instantaneous velocity: it is the actual velocity of the car. To find it we have to find the displacement over a very small time interval. The smaller the time interval, the closer we get to an instantaneous value

    11. DESCRIBING MOTION Acceleration is a vector quantity which refers to “the rate of change of velocity”. average acceleration= change in velocity (m s-1)/ time taken (s) The change in velocity may be a change in speed, or direction or both.

    12. DESCRIBING MOTION DISPLACEMENT-TIME GRAPHS The gradient of a displacement-time graph gives us the velocity. The steeper the gradient, the greater the velocity.

    13. DESCRIBING MOTION VELOCITY-TIME GRAPHS The gradient of a velocity-time graph gives us the acceleration. The area under a velocity-time graph also gives us the displacement.

    14. DESCRIBING MOTION GRAPHS INDICATING +/- VELOCITY AND ACCELERATION

    15. DESCRIBING MOTION DESCRIBING MOTION WITH EQUATIONS

    16. DESCRIBING MOTION VERTICAL MOTION UNDER GRAVITY FREE FALL: An object is in ‘free fall’ if the only force acting on it is the gravity. All the objects in free fall accelerate downwards at the same rate. a= - g = - 9,8 ms-2

    17. DESCRIBING MOTION VERTICAL MOTION UNDER GRAVITY TERMINAL VELOCITY: On Earth, falling object always experience some Air Resistance. The air resistance is not constant, it increases with speed. Eventually the air resistance and weight will balance out. At this point the object stop accelerating and is travelling at the maximum possible speed or terminal velocity.

    18. DESCRIBING CIRCULAR MOTION Uniform circular motion is the motion of an object in a circle with a constant or uniform speed. An object moving in uniform circular motion would cover the same linear distance in each second of time. The distance of one complete cycle around the perimeter of a circle is known as the circumference

    19. DESCRIBING CIRCULAR MOTION MEASURING ANGLES Radian The word radian describes a certain size of an angle. For an angle of one radian the arc length along the edge of the circle is equal in length to the radius. If you want to know the exact size of the radian in terms of degrees, take 360 and divide it by 2 times pi. That number is how many degrees there are in a radian. How many radians are there in a circle? 1 circle= 360º= 2p rad

    20. DESCRIBING CIRCULAR MOTION TIME PERIOD AND FREQUENCY TIME PERIOD (T) It is the time (s) for a complete rotation FREQUENCY It is the number of rotations per second (Hz) T= 1/f

    21. DESCRIBING CIRCULAR MOTION ANGULAR SPEED For an object rotating about an axis, every point on the object has the same angular speed. Angular speed has the units rad/s. Angular speed is the rate of change of angular displacement and can be described by the relationship w=q/t We can also calculate the angular speed if we know the time period or the frequency of the motion. w=q/t = 2p/T= 2pf

    22. DESCRIBING CIRCULAR MOTION LINEAR SPEED We can calculate the linear speed at any instant: v=s/t LINKING v AND w Speed=distance/time taken v= 2pr/t= w.r

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