The key is understanding Newton's First Law of Motion:

* An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Let's break down the scenarios:

* If the body is initially at rest: Applying a constant force will indeed cause it to accelerate (change its velocity) and move with increasing speed.

* If the body is already in motion:

* If the force is applied in the same direction as the motion: The body will continue to accelerate, increasing its speed.

* If the force is applied in the opposite direction of the motion: The body will decelerate (slow down).

* If the force is applied perpendicular to the motion: The body will change direction while maintaining its speed.

Uniform speed requires a *balanced* force:

* For an object to move with *uniform speed*, the net force acting on it must be zero. This means the constant force you apply needs to be balanced by an equal and opposite force (like friction, air resistance, or another applied force).

In summary:

* A constant force alone does *not* guarantee uniform speed.

* A constant force will cause acceleration if it's the only force acting on the object.

* For uniform speed, the net force on the object needs to be zero.

Let me know if you'd like any examples or further clarification!