Well... if something changes, it can't be called a constant. And the effects appear not at the speed of light, but when you approach it. What changes is: the time; distances in the direction of travel; the mass of the travelling object.
A constant in an experiment is the object or value that does not change through out the experiment.
the force or other moving object
An unbalanced force can: change the speed an object moves at change the direction an object is moving cause an object to start/stop moving
density
Change of position relative to another object
force can change the shape and size of an object force can change the direction of an moving object force can make a stationary object move and make a moving object move faster force can slow down or completely stop a moving object
Change of position relative to another object
how does moving a fulcrum on a lever change the amount of force needed to move an object
Speed or direction or both.
A variable is a named object that is mutable. A constant is a named object that is immutable.
Balanced forces will not change the velocity - speed and direction - of a moving object. the object will continue to move in the same way.
Slows it.