MOTION

MOTION
Motion involves a change of position of a body with time. It also involves how things move and what makes them to move.
There are two forms of motion:
Kinematic motion which is the description of how objects move without regard to force that causing their motion and dynamic motion which deals with why objects move as they do.
TYPES OF MOTION
a        RANDOM MOTION: This irregular or disorder movement of object with no preferred direction. Examples are Brownian motion (irregular motion of particle of various kind suspended in water, movement of football player on the field, movement of particle suspended into the air etc.
b      TRANSLATIONAL MOTION: When rigid objects move from one place to another without rotating, the motion is said to be translational. Examples are the movement of a car traveling from Sagamu to Lagos, movement from one wall of class room to another etc.
c       ROTATIONAL MOTION: This is when a body in moving in circular form about its axes. Examples are earth rotation, the wheels of a moving car, and the rotation of the blades of an electric fan etc.

d       OSCILLATORY OR VIBRATORY MOTION: This is when a body moves to and fro. Examples are motion of rocking chair, the motion of a pendulum as it swings back and forth, a diving board, the string of a plucked guitar, the vertical movement of a disturbed mass in a spiral spring etc.

RELATIVE MOTION
Relative motion is change in position of a body with respect to another body.  Since the earth is always in motion, we can conclude that all motions are relative with respect to the earth. Relative motion is the calculation of the motion of an object with regard to some other moving object. Thus, the motion is not calculated with reference to the earth, but is the velocity of the object in reference to the other moving object as if it were in a static state. For example, a person sitting in an airplane is at zero velocity relative to the airplane, but is moving at the same velocity as the airplane with respect to the ground.
For example,
(i)                 Let us consider two vehicles P and Q travelling side by side at the same speed. To the passengers in the vehicle P, the vehicle Q will appear stationary. This means that the motion of each vehicle relative to the other is zero.
(ii)                Let us consider the case where vehicles P and Q travel in the same direction with velocities 40 kmh-1 and 60kmh-1 respectively. The speed of Q relative to P is
60 – 40 = 20kmh-1. What this means is that we can imagine that P is at rest and Q travels with a velocity of 20 kmh-1.
(iii)              Consider the situation when the two vehicles P and Q are moving in opposite directions, then the velocity of Q relative to P will be 60 + 40 = 100 kmh-1.

SCALARS AND VECTORS
(a)    SCALAR QUANTITIES: These are types of quantity that have only magnitude. Examples are length, mass, distance, volume, density, time, speed, temperature etc.
(b)   VECTOR QUANTITIES: These are types of quantity that have both magnitude and direction. Examples are velocity, displacement etc.
PARAMETERS OF MOTION
(i)DISPLACEMENT: This is a distance traveled in a specific direction. For example, if someone travels a distance of 10 m eastward, it is a vector quantity and measured in meter.
(ii)SPEED: This is the rate of change of distance with time. It is a scalar quantity and its S.I. unit is m/s or ms-1.
                                                Speed = (distance)/time 
                                                               
(iii)UNIFORM OR CONSTANT SPEED: This occurs when a body covers equal distance in equal time intervals, no matter how small the time interval.
(iv)VELOCITY: This is defined as the speed in a specified direction or the rate of change of displacement with time. It is a vector quantity and its S.I. unit is m/s or ms-1.
                                                Velocity = (displacement)/time 
                                                                      
(v)UNIFORM VELOCITY: This occurs when a body travels equal displacement in equal time intervals, no matter how small the time interval.
(vi)INSTANTANEOUS VELOCITY: This is defined as the Velocity at any instant of time. The speedometer of moving vehicles indicates instantaneous Velocity.
(vii)ACCELERATION: This is defined as the rate of change of Velocity with time. It is a vector quantity and it S.I. unit is m/s2 or ms-2.
Acceleration = (velocity)/time 
                                                                           
(vii)UNIFORM ACCELERATION: This occurs when the velocity of a moving body increases by equal amount in equal interval of time, no matter how small the time interval.
(viii)RETARDATION OR DECCELERATION: This occurs when the velocity of a moving body decreases with time.

 WORKING EXAMPLES
1.      A car travels at an average speed of 360 kmhr-1. What distance does it cover in 5 minutes?
Solution
Conversion of  km/hr to m/s
360 km/hr = (360 x 1000)/60 x 60    = 100 m/s.
                     
Conversion of minutes to seconds
5 minutes = 5 x 60 = 300.
Therefore,
Speed = (distance)/time 
             
Distance = speed x time.
Distance = 100 x 300
Distance = 3,000 m = 30km.
2.      A car moves from a velocity of 20m/s to a velocity of 30m/s in 5 seconds. What is the average acceleration of the car?
SOLUTION
Acceleration = (velocity)/ time  = (final velocity – initial velocity)/time
                                                    
Acceleration = (30 – 20)/5   =   10/5   = 2 ms-2.
DISTANCE (OR) DISPLACEMENT TIME GRAPH
This is a graph in which distance or displacement is plotted against time. Distance is plotted on the vertical axis and time is on horizontal axis. The slope or gradient of the graph is speed or velocity.       
  
VELOCITY – TIME GRAPH
This is a graph of velocity plotted against time. The gradient of the graph is acceleration. For example, if an object travels along a straight path and has the following velocities for the first 12 seconds of its motion,
Velocity(m/s)
0.0
10.0
20.0
20.0
15.0
10.0
5.0
0.0
Time (s)
0
10
20
30
40
50
60
70
The velocity – graph is given as;

CAUSES OF MOTION (FORCE)
Force is an agent that change or tend to change the state of rest or of uniform motion in a straight line of body. It is a vector quantity. And its S.I. unit is Newton (N).
TYPES OF FORCE
(i)                 Contact Force: This is a type of force which are in contact or in touch with the body to which they are applied. Examples are Force of push or pull, tension, reaction, frictional force etc.
(ii)               Force field: These are forces whose sources do not require contact with the body to which they are applied. Examples are Gravitational force, magnetic force etc.

Comments

Post a Comment

Popular posts from this blog

PROJECTILES

Image
THE CONCEPTS OF PROJECTILES Let us consider a boy who releases a piece of stone from his catapult against a bird on a tree branch, the stone will travel in parabolic path towards the bird. Likewise if we throw a tennis ball against a wall, the path of the ball towards the wall is a parabola. On hitting the wall, the ball returns to the ground also along a parabolic path. The same type of curve is seen when a ball is projected horizontally from the top of a building. The stone or ball been projected is known as PROJECTILE . EXAMPLES OF PROJECTILE MOTION (i)                  A thrown rubber ball re – bouncing from a wall. (ii)                An athlete doing the high jump. (iii)              A stone released from a catapult. (iv)              A bullet fired from a gun. MOTION OF A PROJECTILE Let us consider the simple case of a stone thrown horizontally with an initial velocity of u from the top of a high wall of height h. The stone is subject to two independent motions;
Read more

EQUILIBRIUM OF FORCE

Image
EQUILIBRIUM OF FORCES An object is in equilibrium when it is not accelerated, that is there is no force acting on it in any direction. For a body in equilibrium, the forces acting on it are so related in magnitude and direction that no acceleration results. A body is said to be in equilibrium when the body as a whole either remains at rest or moves in a straight line with constant speed and the body is either not rotating at all or is rotating at a constant angular velocity. FORMS OF EQUILIBRIUM      (a) Static equilibrium: This is when a body is at rest or moving with constant velocity. (b) Dynamic or Kinetic equilibrium: This is when a body is moving with a constant velocity in a straight line or rotating with a constant angular velocity about a fixed axis through its centre of mass. This means that the forces that set the body in motion balance the forces that resist the motion. RESULTANT AND EQUILIBRANT FORCES A body acted upon by two or more forces is said to be in
Read more

EQUILIBRIUM OF BODIES IN LIQUID

EQUILIBRIUM OF BODIES IN LIQUID When a heavy object is immersed in a liquid the object appears to become lighter. Consider the experience when a bucket of water is being drawn out of a well. While still under the water the bucket appears very light and becomes very heavy as soon as it is out of water. Archimedes explains this showing that when the bucket still in water, the body is acted upon by an upward force U called upthrust. While still under water, the equilibrium of the bucket is as : T = W – U. Where T =  tension in the rope.            W = weight.             U = upthrust.      U = W – T. It is also known as loss in weight. ARCHIMEDES PRINCIPLE It states that when an object is wholly or partially immersed in a fluid, it experiences a loss in weight or an upthrust which is equal to the weight of the fluid displaced by the object. FLOATING If a body is denser than the liquid, it will completely sink in it, but if the density of the body is less than that
Read more