Question #1d51d
1 Answer
Equations (3) and (5) are the required equations.
Explanation:
There are two kinematic equations connecting velocity and time.
Consider a velocity-time graph of an object which moves with uniform acceleration as shown in Fig below.
Object has initial velocity
We draw perpendicular lines BC and BE from point B on time and velocity axes respectively.
Initial velocity is represented by OA, the final velocity is represented by BC and the time interval
BD = BC – CD, is the change in velocity during time
Draw AD parallel to OC.
In the figure
BC = BD + DC = BD + OA
Now BC =
Therefore we get
#v# = BD +#u#
#=># BD =#v - u# ........(1)
We know that rate of change of velocity is acceleration
#:.a = ("change in velocity")/("time taken")#
#=>a= "BD"/"AD" = "BD"/"OC"#
Since OC =
#a = "BD"/ t#
#=> "BD" = at# .............(2)
From (1) and (2) we get
#v = u + at# .......(3)
From the Fig. the distance traveled
Now
Area of OABC
Substituting OA =
#=>s = u t + 1/2 a t^2 # .......(5)
=.=.=.=.=.=.=.=.=.=.=.=.=.=.=.=.=.=.=.=.=.=
For sake of completeness
Kinematic Equation for Position-Velocity relation is established as follows.
In the velocity-time graph shown in the Fig. above the distance
Area of the trapezium OABC
#= ("OA" + "BC")/2 xx# OC
Substituting OA =
#s = (u + v)/2 xxt # .......(5)
The velocity-time relation (3) can be rewritten as
#t = (v - u)/a# ...........(6)
Substituting value of
#s = (v + u)/2 xx (v - u) /a#
#=>2 a s = v^2 – u^2#