When a body is moving with uniform velocity along a straight line, the gravitational force acting on it remains constant, assuming no other forces are involved. The magnitude of the gravitational force is given by the product of the mass of the body (m) and the acceleration due to gravity (g).
However, when the body suddenly starts to move with constant accelerated motion, the situation changes. The body now experiences an additional force, which is responsible for its acceleration. This force is commonly referred to as the net force or resultant force.
If we assume that the body is subject only to the gravitational force and the net force causing the acceleration, the magnitude of the net force (F_net) is given by Newton's second law of motion: F_net = m * a, where m is the mass of the body and a is the acceleration.
In this scenario, the gravitational force acting on the body does not change instantaneously when the body starts accelerating. The gravitational force remains the same, while the net force becomes greater than the gravitational force to provide the necessary acceleration. As the body accelerates, the net force gradually becomes equal to the gravitational force, and the body reaches a state of equilibrium with a new constant velocity under the influence of both forces.
To summarize, the gravitational force on a body moving with uniform velocity along a straight line remains constant, but when the body suddenly starts to move with constant accelerated motion, the net force becomes greater than the gravitational force to provide the necessary acceleration.