Page 159 - WCS - Electrical

P

θ
Q.Sin
=
α =
tan
AC
Q
θ

P
BC
AC =
P×
AC
Distance
QxBC
P = Q× BC Q = BC Speed = P + Q.cos covered
Time
AC
direction
Distance

Definite
PxAC WORKSHOP CALCULATION & SCIENCE - CITS
P = Velocity =
BC Time

2
CD a = Acceleration m/sec (positive value)
Sin θ =
R = Retardation m/sec (negative value of acceleration)
Q a = change in velocity m/sec 2 2
Time
BD Equations of motion
Cos θ =
Q Then v = u + at
1
2
2
2
2 2 s = ut at and v – u = 2as
2
R = P + Q + 2.P.Q cos θ v = u + 2as
2
2
CD CD Retardation 

−u)
 (v
tan α = = F = m  
OD OB + BD When the body has its initial velocity lesser than its final velocity it is said to be in acceleration. When the final
t


velocity is lesser than the initial velocity the body is said to be in retardation.
Q.Sin θ Then the three equation of motion will be
=
P + Q.cos θ v = u – at
Q.Sin θ s = ut – at 2
tan α =
P + Q.cos θ u2 –v2 = 2as
Average speed
2 2 Vm - Average speed in metre/min, (metre/sec)
R = P + Q + 2.P.Q cos θ
n - Revolutions per minute or number of strokes per minute
s - Distance travelled, length of stroke.
Motion under gravity
A body falling from a height, from rest, has its velocity goes on increasing and it will be maximum when it hits the
ground. Therefore a body falling freely under gravity has a uniform acceleration. When the motion is upward, the
body is subjected to a gravitational retardation. The acceleration due to gravity is denoted with ‘g’.
Momentum
It is the quantity of motion possessed by a body and isequal to the product of its mass, and the velocity with which
it is moving. Unit of momentum will be kg metre/sec.
Momentum = mass x velocity
Newton’s laws
First law
Every body continues to be in a state of rest or of uniform motion in a straight line unless it is compelled to change
that state of rest or of uniform motion by some external force acting upon it.
Second law
The rate of change of momentum of a moving body is directly proportional to the external force acting upon it and
takes place in the direction of the force.
Third law
To every action there is always an equal and opposite reaction.
Law of conservation of momentum
When two moving bodies have an intentional or unintentional impact, then sum of the momentum of the bodies
before impact = sum of the momentum after impact, or the change in momentum after the impact is zero.
m - mass of one body and
1
v - velocity with which it moves m - mass of second body
2
1
v - velocity with which it moves
2

146

CITS : WCS - Electrical - Exercise 13