Derivation of Third Equation of Motion


 
 
Concept Explanation
 

Derivation of Third Equation of Motion

Derivation Of Third Equation Of Motion: It is also known as Equation for Position-Velocity Relation (Third Equation)

The distance travelled by a uniformly accelerated body in time t is given by the area of the space enclosed between the velocity-time graph with time axis.

So, distance travelled, s = area of the trapezium OABC

s=frac{sum;of;parallel;sides}{2}times distance; between;parallel;sides

s=frac{(OA+BD)}{2}times OD

But OA = u, BD = v and OD = t

Substituting the above values, we get

s=frac{(u+v)t}{2}                ....(v)

From equation v = u + at, we get

t=frac{v-u}{a}                    ..... (vi)

Substituting the values of t in Eq. (v), we get

s=frac{(u+v)(v-u)}{2a};;;Rightarrow ;;;s=frac{v^{2}-u^{2}}{2a}

v^{2}-u^{2}=2as

Hence, the third equation of motion is derived.

 

 
 


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