Question

Why the force is not required to move a body uniformly along a straight line path?

Answer 1

We know that
F = ma
The above equation is central equation of Newton's first law and states that force acting on a body produces an acceleration in it. In other words, a net force causes change in velocity.
so,
F = m(dv/dt)
Thus, if a body is moving with constant velocity
dv/dt = 0
so,
the net force acting on it will be zero.
Thus,
A force is required to change the velocity of an object. Here object is moving uniformly i.e constant velocity, so no force is required.