Explanation: Derivation Of Equation Of Motion It is first important to understand what is motion and its laws to understand the derivations better. Following is the table explaining more concepts related to motion Introduction to Motion Equation Of Motion And Its Application Derivation of Equation of Motion There are mainly three equations of motion which describe the relationship between velocity, time, acceleration and displacement. First, consider a body moving in a straight line with uniform acceleration. Then, LET the initial velocity be u, acceleration be a, time period be t, velocity be v, and the distance travelled be S. The equation of motions derivation can be done in three ways which are: Derivation of equations of motion by Simple Algebraic Method Derivation of Motion by Graphical Method Derivation of Motion by Calculus Method Below, the equations of motion are derived by all the three methods in a simple and easy to understand WAY. Derivation of First Equation of Motion The first equation of motion is: v = u + at Derivation of First Equation of Motion by Algebraic Method It is known that the acceleration (a) of the body is defined as the rate of change of velocity. So, the acceleration can be written as: a = v − ut From this, rearranging the terms, the first equation of motion is obtained, which is: v = u + at Derivation of First Equation of Motion by Graphical Method Consider the diagram of the velocity-time graph of a body below: Derivation Of Equation Of Motion In this, the body is moving with an initial velocity of u at point A. The velocity of the body then changes from A to B in time t at a uniform rate. In the above diagram, BC is the final velocity i.e. v after the body travels from A to B at a uniform acceleration of a. In the graph, OC is the time t. Then, a perpendicular is drawn from B to OC, a PARALLEL line is drawn from A to D, and another perpendicular is drawn from B to OE (represented by dotted lines). Following details are obtained from the graph above: The initial velocity of the body, u = OA The final velocity of the body, v = BC From the graph,BC = BD + DC So, v = BD + DC v = BD + OA (since DC = OA) Finally, v = BD + u (since OA = u) (Equation 1) Now, since the slope of a velocity-time graph is equal to acceleration a, So, a = slope of line AB a = BD/AD Since AD = AC = t, the above equation becomes: BD = at (Equation 2) Now, combining Equation 1 & 2, the following is obtained: v = at + u Derivation of First Equation of Motion by Calculus Method It is known that, Derivation Of Equation Of Motion So, Derivation Of Equation Of Motion Derivation of Second Equation of Motion The second equation of motion is: S = ut + ½ a2 Derivation of Second Equation of Motion by Algebraic Method Consider the same notations for the derivation of the second equation of motion by simple algebraic method. Derivation Of Second Equation Of Motion Derivation of Second Equation of Motion by Graphical Method Taking the same diagram used in first law derivation: Derivation Of Equation Of Motion In this diagram, the distance travelled (S) = Area of figure OABC = Area of rectangle OADC + Area of triangle ABD. Now, the area of the rectangle OADC = OA × OC = ut And, Area of triangle ABD = (1/2) × Area of rectangle AEBD = (1/2) at2 (Since, AD = t and BD = at) Thus, the total distance covered will be: S = ut + (1/2) at2 Derivation of Second Equation of Motion by Calculus Method It is known that v = dS/dt.‘ So, Derivation Of Equation Of Motion Derivation of Third Equation of Motion The third equation of motion is: v2 = u2 + 2aS Derivation of Third Equation of Motion by Algebraic Method Derivation Of Third Equation Of Motion Derivation of Third Equation of Motion by Graphical Method Derivation Of Equation Of Motion The total distance travelled, S = Area of trapezium OABC. So, S=(SumofParallelSides)×Height2 S=(OA+CB)×OC2 Since, OA = u, CB = v, and OC = t The above equation becomes S=(u+v)×t2 Now, since t = (v – u)/ a The above equation can be written as: S=(u+v)×(v–u)2a Third equation of motion is obtained by solving the above equation: v2 = u2+2aS Derivation of Third Equation of Motion by Calculus Method It is known that, Derivation Of Equation Of Motion These were the detailed derivations for equations of motion in the graphical method, algebraic method and calculus method