3.0 MOTION AND FRICTION

   Many scientist have studied motion and its properties because its importance to life. The italian, Galileo Galilei, who lived from 1564 to 1642, did the first systematic study of motion. Also sir Isaac Newton did more detailed work on the study of motion.

   Motion involves a change of position of a body with time. It also involves how things move and what make them to move. It exist in different forms and occurs in solid, liquid, and gases. Motion is define as the change of position of a body with time.

3.1 TYPE OF MOTION

[1] RANDOM MOTION: this is the type of motion which a body moves in a non-linear manner and changes direction continuously. Example; (Molecular movement in gas, Dashing of object in air)

[2] TRANSLATIONAL MOTION: this is the type of motion which occurs when an object moves in a fixed direction. When a body move from point A to point B, the body is said to be translated from A to B. Example; (Movement of car, Movement of human)

   A________________B

[3] ROTATIONAL MOTION: This is the movement of a body in a rotational manner about its axis. Example (Fan blade, Wheel of car, Rotation of earth)

[4] OSCILLATORY MOTION: This is a to and fro movement about a fixed point. it arises due to a slight displacement of an object from the initial position to a new position and back tho the initial position. Example; (Simple pendulum, Punching a bag)

[5] RELATIVE MOTION: this is the motion of an object in relation to another body. Example (Pulling on a spinal spring, bending a ruler on a beam).

3.2 CAUSES OF MOTION

   Forces cause motion. when force is applied on any object, it causes change.

   

3.2.1 TYPE OF FORCE

[1] Contact Force: This exist when there is a touch, hold or a contact with the object in questions. it is further divided into (i) Like force [push] (ii) Unlike force [pull] (iii) Fractional force.

[2] Field Force: This exist in or is confined to a given region or space, i.e a region in space where a body experience the effect of a force which occurs as a result of the influence of some physical agencies. its divided into

   (a) Magnet force: force that attract magnetic substance, e.g nails toward a magnet.
   (b) Gravitational force: force that attract or pull object irrespective of their masses toward center of the earth's surface
   (c) Electric force: force that keep current (negatively charge particles) through a conductor of elctricity.

    Experiment: Using the effect of magnet on nail to show force field, a bar magnet is taken and put on a table and sheet of paper is taken to cover it. Nails are then spread on the sheet of paper.

   Conclusion: The pattern of the field is seen from the settings of the nails on either the bar magnet. On the bar magnet, the nails are seen to be in an order of arrangement in which the field is greater at the pole than in the middle.

3.3 FRICTION

   When a body slides over the surface of another body, there is an opposing force acting opposite to the direction of motion. This opposing force is called friction. Thus, Friction can be define as a form of force that opposes the relative sliding motion of objects in contact with surface. it is a vector quantity which exist in "solid, liquid and gas"

3.3.1 LIMITING FRICTION

   When a body is placed over another, a force act between the surface in contact and this force is called limiting friction.

   ADVANTAGES OF FRICTION

   (1) The tyre of a motor car and a bicycle are made rough to increase friction.
   (2) Without friction, the brake of a motor car cannot work.
   (3) Without friction between the feet and the ground, it will not be possible to walk without falling.
   (4) Friction helps in the roataion of the various part of the machine.
   (5) When ground is slippery after rain, it is made rough by spreading sand in order not to cause slipping.

   DISADVANTAGES OF FRICTION

   (1) It reduce motion.
   (2) It causes wear and tear in machine.
   (3) It reduce the efficiency of machine.
   (4) It causes the heating of engines.

3.4 METHOD OF REDUCING FRICTION

   1. Streamlining: is used to reduce friction due to the shape of an object which ensures that only a small surface area of the object is in head-on contact with the field. Example; Aeroplane, ship.

   2. Ball Bearing: Shafts are fixed on ball bearing so that friction will reduce because rolling friction is less than sliding friciton. it is provided in (shafts of motor, axle of motor).

   3. Lubricating: is viscous liquid or oil which are applied between two surface contact. Example; Lubricating of wheels.

   4. Polishing: friction between two surfaces in contact can be reduced by polishing them. Example; Jewel bearing in watches.

   5. Use of pencil and polysterene.

   6. Banking.

3.5 LAWS OF SOLID FRICTION

   1. It opposes motion
   2. The limiting fractional force is independent of the surface area in contact.
   3. The ratio of F/R is practically constant between any two surface.
   4. The limiting fractional force is directly proportional to the normal reaction between any two surface.
   5. The limiting fractional force depends on the nature of the surface in contact
   6. The limiting fractional force is independent of the relative velocity between the surface.

3.6 CIRCULAR MOTION

   Circular motion is a motion in a circular path in which speed of the body remains constant while its direction contineously changes. e.g;

   i. Stone whirled in horizontal circle
   ii. Planets going round the sun
   iii. The earth moving round the sun


 

 [1] What is motion ?
 [2] Explain type of motion
 [3] What is relative motion
 [4] State the causes of motion
 [5] Expain limiting friction
 [6] State the law of solid friction and its application
 [7] State and explain method of reducing friction
 [8] What is circular motion
 [9] Define angular velocity and derived the fomlular
 [10] Give advantages and disadvantages of friction
 

 


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