Question
The acceleration (a) of a body moving along x-axis is given by a=4x3 ,where a is in m/s2 and x is in metre.if at x=0 the velocity of body is 2m/s,then find its velocity at x=4m?
Joshi sir comment
a = 4x3
so dv/dt = 4x3
or dv/dx * dx/dt = 4x3
or dv/dx * v = 4x3
or vdv = 4x3dx
or ∫vdv = 4∫x3dx
or v2/2 = 4x4/4 + C
at x = 0, v = 2
so 4/2 = 0+C
so C = 2
on putting the value of C
we get v2/2 = x4+ C
now put x = 4 and get v