Mechanics are classified into statics and dynamics.
statics:it deals with bodies at rest under the action of forces
dynamics:dynamics deals with bodies under motion and it is further classified into kinematics and kinetics
kinematics :it deals with the motion of bodies without considering the cause of motion.
kinetics :it deals with the motion of bodies considering the cause of their motion
scalars and vectors: all physical quantities can be classified into scalars or vectors
Physical quantities that can be completely specified by means of a numerical value and a unit, thus said to have only magnitude are called scalars examples :mass,distance, time, speed, densityand temperature
pphysical quantities that can be defined only if both magnitude and directionare specified are called vectors examples:displacement, force, velocity, acceleration, etc.
Geometrical representation of a vector :a line segment can be represented by a line segment with a arrow head.
1.the length of the line segment (AB)is propotional to the magnitude of the vector.
2.the arrow head indicates the direction of the vector.
Distance and displacement :
distance :distance is defined as the length of the actual path described by a particle in motion. The unit of distance is measured by centimeters and meters .it is a scalar quantity
displacement: displacement is defined as the shortest distance between the initial and final positions of a body .it is vector quantity
speed:speed is defined as the rate at which a particle covers a distance along a given path. It is given in the ratio of distance travelled to the time taken speed =distance travelled(s)/time (t).
instantaneous speed:the speed of a particle at a given instant is known as instantaneous speed. The speedometer of a vehicle indicates the instantaneous speed of the vehicle .
uniform speed:a body or particle is said to possess uniform speed if it travels equal distances in equal intervals of time.
variable speed:defined as the ratio of the total distance travelledto the total time taken by the particle to cover the distance.
Average speed =total distance /total time
velocity :it is displacement of a body in unit time or rate of displacement.
Velocity =displacement /time.
UNIFORM AND NON UNIFORM VELOCITY : a body in motion is said to move with uniform velocity if it has equal displacements in equal intervals of time,however small thelse intervals may be.if a body covers unequal displacements in equal intervals of time (or equal displacements in unequal intervals of time),it is said to be moving with non uniform velocity.
INSTANTANEOUS VELOCITY :it is the ratio of total displacement of total taken.
Average velocity =total displacement/total time.
ACCERALATION:a particle moving with variable velocity is said to be possess acceleration. When a particle executes non uniform, it’s velocity changes. Acceleration is defined as the rate of change of velocity.
Acceleration =change in velocity /time