Introduction-We see different things in motion people and vehicle move on road.
Things are in motion inside our body too.e.g blood moves in our body.
The different kinds of motion around us appear to be very different. But they are follow same set of rules.
Rest and motion:-
If the position of an object does not change with respect to time, it is said to be at rest.
If the position of an object does change its position with respect to time, it is said to be at motion.
Types of motion:-
Linear motion- If the object moves in a straight path, the body is said to be in linear motion.e.g motion of a moving car on a straight path.
Circular (or rotational) motion-An object moving in a circular path around a fixed point, the body is said to be in circular (rotational) e.g.an insect moves along a circular path.
Vibratory motion- A body moves to and fro about a fixed point,( called mean or equilibrium position) then the body said to be in vibratory motion.e.g pendulum of a wall clock.
Motion is relative-When a person sitting in a train the distance from other passenger does not change i.e with respect to other passenger your position does not change. You are in rest.
But the person sitting inside the train changes its place where the train is moving as the time passes i.e with respect to place you are moving at the same time. So motion is not absolute, it is relative.
Describing motion -We measure the motion or rest of an object with the help of a fixed point known as reference point.
Reference point-A fixed point or fixed object with respect to an object change its place is known as reference point or origin.
N:B-->A object is in motion or rest at same time with two different reference point of observation. So, rest and motion are relative terms.
Motion along a straight line-
Position of an object moving along a straight line is described by a quantity 'x'. The sign of'x' denotes whether the object moves in positive or negative direction.
Scalar and vector quantities-
A quantity which has only magnitude is known as a scalar quantity example volume ,density.
Quantity which has both magnitude as well as direction is known as vector quantity example displacement, velocity etc
Distance and displacement-
Distance-Length of actual path between two points in the given interval of time is known as the distance travelled by the body.
Displacement-Shortest path between two point with direction is known as the displacement of the body at given interval of time.
N:B→ Displacement of an object may be zero but distance can never be zero.
Distance travelled by an object is may be equal or greater than the displacement of the object.
Uniform and Non uniform motion-
Uniform motion-If a body moves in a straight line and it covers equal distance at equal interval of time, it is said to be in uniform motion example a car cover 10 km in per hour motion of a car is uniform motion.
Non uniform motion-If a body moves and cover an unequal distances in equal interval of time, it is said to be in in non uniform motion example A man is travelling on a road
Speed- It is measuring rate of motion of an object.
It is defined as the distance covered by it per unit time.
Speed (v)=distance / time or
v=s/t
Unit of speed=unit of distance/unit of time
S.I unit metre/ second (ms^-1)
C.G.S system centimetre/ second (cms^-1)
Type of speed:-
Uniform speed or constant speed- An object cover equal distance in equal interval of time then the object is said to be in uniform or constant speed.
Non uniform speed or variable speed-An object covers unequal distance in equal interval of time then the object is said to be non uniform or variable speed.
Average speed-Ratio of total distance covered by it to the total time taken by it.
Vav=total distance travelled / total time taken
Instantaneous speed- Speed of a object at any instant during its motion is called instantaneous speed. It is measured by speedometer.
Velocity (speed of a body with direction)
Velocity- Velocity of an object is define as the displacement of the body per unit time.
Expression for velocity
velocity=displacement / time
v=s/t
Unit of velocity = unit of displacement/unit of time
SI unit metre/second(m s^-1)
CGS system centimetre/second(cms-1)
Types of velocity-
Uniform velocity or constant velocity-Velocity of an object is said to be in uniform velocity, if it covers equal displacement in equal interval of time.
Non uniform or variable velocity- Velocity of an object is said to be non uniform velocity if it covers an unequal displacement in equal interval of time example a stone thrown vertically upward.
Average velocity-Ratio of the total displacement of a body to the total time taken.
Average velocity (Vav)=total displacement of the body/total time taken.
N:B->velocity of a body changes by changing the direction and speed of the body.
velocity of a car moving on a zigzag road changes as its both directions to the motion change.
Acceleration ( rate of change of velocity)
Acceleration acceleration of a body or an object is defined as the change in velocity per unit time.
Acceleration=change in velocity/ time Taken
Acceleration is a vector quantity
Expression for acceleration
Acceleration=change in velocity / time taken
Acceleration= final velocity - initial velocity / time taken
a=v-u/t
N:B an object can have zero acceleration but non zero velocity.
unit of acceleration = unit of velocity/unit of time
SI unit ms^-2
CGS system cms^-2
Deceleration-if the speed of an object decreases, we say that it is the deacelerating, or it has deceleration or retardation .
if the acceleration direction is opposite to that of velocity the object will decelerate
Uniform acceleration-velocity changes by an equal amount in equal interval of time then the acceleration of an object is known as uniform acceleration example free falling is thrown from the top of a tower
Non uniform acceleration-velocity changes by an unequal amount in equal interval of time example motion of a bus leaving the bus stop
Graph-A graph is a very powerful method of presenting information .
Speed from distance time graph-if the graph is a straight line, speed of object is equal to slope of the straight line
more steeply inclined distance time graph indicate greater speed
Distance time graph for non uniform speed-graph is not a straight line.
Speed time graph-an object moves with constant speed, its graph is a straight line.
Velocity time graph area under graph gives displacement.
Acceleration from velocity time graph- acceleration is uniform, graph is a straight line.
Slope of graph gives acceleration along a straight line
Equation for motion with the help of graph
Point A and B on the graph represent that time 0 and t respectively
Where is the tree of particle at time t=0,OA represent u
Velocity of the particle at time t is v,OD represent v
Drop the perpendicular BE on time axis
Draw the perpendicular AC on BE.
FIRST EQUATION OF MOTION
FOR LINE AB, SLOPE= BC/AB
a=BC/AC
a=BE-CE/EC
a=OD-CE/OE
a=v-u/t
at=v-u
v=u+at
This equation is known as velocity time equation.
SECOND EQUATION OF MOTION-Area under velocity time graph gives displacement
s= area of OABE
Area of rectangle OACE+area of triangle ABC
(OA)•( OE )+1/2(AC)•(BC)
(OA)•(OE)+1/2(OE)•(BC/AC×AC)
(OA )•(OE )+1/2(OE)( BC/AC×OE) [AC=OE]
(OA)• (OE) 1/2(BC/AC)(OE)^2
where OA=u, OE=t, BC/AC=slope=a
S=ut+1/2at^2
This is also known as displacement time equation.
THIRD EQUATION OF MOTION-AREA OF TRAPEZIUM =1/2(SUM OF PARALLEL SIDE)×( DISTANCE BETWEEN THEM)
s= 1/2(OA+EB)•( AC)
s=1/2(OA+OD)•( AC/BC× BC)
s=1/2(OA+OD)•( BC-CE/BC/AC)
s=1/2(OA+OD)• (OD-OA/BC/AC)
s=1/2(OD^2-OA^2/BC/AC)
s=1/2(v^2-u^2/a)
2as=v^2-u^2
v^2=u^2+2as
This is also known as velocity displacement equation
Average velocity for uniform acceleration motion
Average velocity=displacement/time
s/t=it+1/2at^2 /t
s/t=u+(at/2)
s/t=u+(v-u/2). [v =u+at]
Vav=(u+v/2)
N.B Displacement time graph for uniform accelerated motion = curve is known as parabola
Circular motion-An object is moving in a circular path around a fixed point is known as circular motion of that object
Uniform circular motion -Circular motion of an object having constant or uniform speed is known as uniform circular motion
It is also known as accelerated motion
Some differences
Some important facts
Branch of physics which deals with motion is called mechanics
in mechanics where cause of motion is not considered is called kinematics
Locomotion is known as motion of animals
External force is required for the motion of of non living object
When an object is in circular motion,direction of velocity changes to the tangent of the circular path of that object
Odometer is a device used to measure the distance travelled by the vehicle
in uniform motion distance covered by an object is directly proportional to the time taken
In a circular path,acceleration towards the centre is known as centripetal acceleration, centripetal means centre seeking
0 Comments