explain uniform and non uniform accelaration by velocity time graph
Answers
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Answer:
The equation of motions from the velocity-time graph:
The velocity-time graph for a body under uniform acceleration is shown in the figure.
Let initial velocity of the body = u
The final velocity of the body = v
Time is taken by the body = t
Acceleration of the body = a
Derivation of the first equation of motion:
According to the definition,
Acceleration of a body = Rate of change of velocity i.e. slope of the velocity-time graph.
The velocity-time graph for a uniformly accelerated body is given by the straight line AB. So, acceleration of the body is equal to the slope of the line AB.
Acceleration = Slope of line AB =
AD
BD
=
AD
BC−DC
From the velocity time graph,
BC=v,DC=OA=u,AD=OC=t
Then, a⇒
t
v−u
⇒at=v−u⇒v=u+at
⇒ First equation of motion
Derivation of the second equation of motion
Under the uniform acceleration, from the figure, one can write
Distance travelled (s) = Area of trapezium OABC
S = Area of the triangle ABD + Area of rectangle OADC
=
2
1
×AD×BD+OC×OA
Here, AD=OC=t
and BD=BC−DC=v−u
BD=u+at−u=at and OA=u
∴s=
2
1
×t×at+t×u⇒s=ut+
2
1
at
2
This is second equation of motion.
Derivation of third equation of motion
Distance travelled, s = Area of the trapezium OABC
s=
2
1
(Sum of the parallel sides) × Perpendicular distance between the two parallel sides
s=
2
1
×(OA+BC)×OC
s=
2
1
(u+v)×t But a=
t
v−u
⇒t=
a
v−u
⇒s=
2
1
(v+u)×
a
v−u
⇒s=
2a
v
2
−u
2
⇒v
2
−u
2
=2as⇒ Third equation of motion.
Explanation:
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