If an object is not accelerating, then the net force acting on it must be zero. This means that the vector sum of all the forces acting on the object must be zero.

In other words, for an object to be in equilibrium, the forces acting on it must be balanced.

Here are some examples of forces that can act on an object without causing it to accelerate:

- Gravitational force: The gravitational force is the force of attraction between two masses. If an object is on the ground, the gravitational force of the Earth pulls it down. However, if the object is also supported by a surface, such as a table, the normal force of the surface pushes up on the object. These two forces cancel each other out, resulting in no net force and no acceleration.

- Frictional force: The frictional force is the force that opposes the motion of an object when it is in contact with another surface. If an object is moving on a horizontal surface, the frictional force of the surface opposes the motion of the object. However, if the object is not moving, the frictional force is zero.

- Air resistance: Air resistance is the force that opposes the motion of an object through the air. If an object is moving through the air, the air resistance of the air opposes the motion of the object. However, if the object is not moving, the air resistance is zero.