Motion is defined as the change in position of an object over time. There are different types of motion including translational, rotational, random, and oscillatory. Relative motion describes the velocity of one object compared to another. Force is what causes motion, including contact forces like pushes and pulls, and field forces like gravity and magnetism. Circular motion involves constant or changing rotation around a central point and can be described using formulas involving parameters like angular velocity, linear speed, and centripetal force. Centrifugal force acts outwardly away from the center of rotation.

1. MOTION IN PHYSICS
PRESENTED BY:SALAHDEEN HI

2. DEFINITION OF MOTION
• Motion is the change of position of a body with time.
• The study of motion without involving the force causing the motion is called kinematics.
• The study of motion of objects and the forces acting on them is called dynamics.

3. TYPES OF MOTION
1. Translational motion: This type of motion occurs when a body moves in a fixed direction without
rotating e.g. A car moving in one direction from one town to another, movement of a man etc. It is
also called rectilinear motion
2. Rotational or Circular motion: This is the movement of a body in a circular manner about its axis
e.g. the movement of car wheels, electric fan blade, earth about its axis etc.

4. 3. Random Motion: This is a type of motion in which a body moves in a zigzag or disorderly manner with no specific
direction e.g. motion to molecules of gasses, butterflies etc.
4. Vibratory or Oscillatory Motion: This is a to and fro or up and down movement of a body about a fixed point e.g.
the simple pendulum, vibration of plucked guitar string, etc.

5. RELATIVE MOTION
• If two bodies, A and B are moving on a straight line, the velocity of A relative to B is found by
adding the Velocity of B revered to the velocity of A. For instance, if a car traveling on a straight
road at 100km/hr passes a bus going in the same direction at 60km/hr., the velocity of the car
relative to the bus is (-60+100) = 40km/hr. If the car and the bus are traveling in opposite direction
with the same velocities of 100km/r and 60km/hr respectively, the velocity of the car relative to the
bus is ( -(-60) + 100) = (60 +100) = 160 km/hr.

6. CAUSES OF MOTION
• All objects will continue in their state of rest unless acted upon by force. Only the application of a
force can cause visible motion. Hence, force causes motion.
• There are two types of force (a) Contact force (b) Field force

7. (a)Contact Force: They are forces that are in contact with the body they affect e.g. tension, reaction
frictional forces, forces of pull & push, viscous force etc.
(b)Field Force: They are forces whose sources do not require contact but the effect of such forces is
felt in a field of the force e.g. electrical force, magnetic, gravitational pull etc.

8. CIRCULAR MOTION
• In physics, circular motion is movement along a circular path or orbit. It can be uniform (i.e. with constant
angular rate of rotation) or non-uniform (i.e. with a changing rate of rotation)
• Formulae for uniform circular motion
• Consider a body of mass (kg), moving in a circle of radius r (m), with an angular velocity of ω (rads-1)
 The angular velocity is w = Ө/t where Ө-angle subtended (rad) & t-time (s)
 The linear speed is v = s/t where s-distance covered (m)
 The linear speed is v = r×ω (m/s)

9.  The centripetal (inward) acceleration is a = r×ω2 = v2/r (m/s2)
 The centripetal force is F = m×a = r×m×ω2 = mv2/r (N)
 The momentum of the body is p = m×v = r×m×ω(kgm/s)
 The moment of inertia is I = r 2×m (kgm2)
 The angular momentum is L = r×m×v = r 2×m×ω = Iω(kg·m2·s−1).
 The kinetic energy is E = ½(m×v2) = ½(r2×m×ω2) = ·p2 (2·m)−1 = ½(I·ω2) = ½(L2) (J).
 The circumference of the orbit is 2πr (m).
 The period of the motion is T = 2πω−1 (s)
 The frequency is f = T−1 (Hz)
(To convert radian from degree 3600=2∏)

10. CENTRIFUGAL FORCE
• Centrifugal force is a force that acts in opposite direction to the centripetal force. Centrifugal force
is an outward force associated with rotation.

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