When a constant force acts on an object, it either accelerates or maintains its velocity. But how is that connected to constant speed?
To answer this question we must first understand what a force is. A force is a vector quantity with both magnitude and direction, making it much more complicated than a scalar, or number. It is measured in newtons and represented by the symbol F. Force can cause an object with mass to change its velocity (which also includes beginning to move from a state of rest), and this acceleration is called the large S in the equation F = ma.
In order for an object to accelerate, the forces acting on it must be unbalanced. This is why an object slowing down tells us that there are unbalanced forces on it. However, if the constant force is the same as the unbalanced force, it doesn’t necessarily need to increase for the object to slow down.
This is why it’s important to understand that if we want an object to maintain its velocity at a certain value, we must apply a constant force to it. In Unity’s physics simulation, we can set this by adding a Constant Force component to a Rigidbody. Linear and angular accelerations will then continue to accelerate at the same rate until the Rigidbody reaches a maximum linear or rotational velocity (which can be changed by setting the properties Rigidbody.maxLinearVelocity and Rigidbody.maxAngularVelocity).
