KINEMATICS AND NEWTONIAN MECHANICS

1. KINEMATICS OF MOTION

2.1 Kinematics of Motion

Kinematics is the branch of mechanics that describes how objects move, without considering why they move. (i.e. force). It deals with concept such;

1.      Position: the location of objects at a given time given as coordinate x(t), y(t), etc

2.      Displacement: change in position =  it is a vector.

3.      Distance: total path length travelled; it is a scalar.

Motion is defined as the change in position of an object with time.

Dynamics deals with the study of the motion of objects and the forces acting on them.

Types of motion:

1.      Rotational (circular) Motion; wheels of a moving car, rotation of the blades of fan

2.      Translational (Linear) Motion; a car moving from point A to point B

3.      Random Motion; flight pattern of a bee, movement of dust particles

4.      Oscillatory Motion; swinging pendulum etc.

5.      Relative motion; A person is moving in a car, nearby objects move backward, thus they are stationary relative to the earth.

Definition

Force:  Force is an agent that produces acceleration in the body on which it acts.

Or it is a phenomenon that change or tends to change the position of the body at rest or in uniform motion.

Force is a vector quantity as it has both direction and magnitude.

For example,

(i)                 To move a football, we have to exert a push i.e., kick on the football

(ii)              To stop football or a body moving with same velocity, we have to apply push in a direction opposite to the direction of the body.

SI unit of force is Newton.

Dimension formula: [MLT^-2]

Types of force

1.      Contact force: These are forces that act on a body directly h a medium. Examples are push, pull, friction, pressure etc.

2.      Non-Contact (Field) force: These are forces that act through spaces without making direct contact with the body. Examples are gravitational force, electrostatic force and magnetic force.

Example calculations:

1.      A car starts from rest and accelerates uniformly at 2.5m/s2 for 10s. calculate

a.       the final velocity of the car,

b.      the distance it travels during this time

2.      A stone is dropped from a height of 45m. Neglect air resistance and take g = 9.8ms2. find

a.       the time it takes to reach the ground

b.      its speed just before it hits the ground