GameObject with rigidbody slowed down if "Use gravity" is tagged?

I have a simple cube on a plane and I want to move it using AddForce(). However if "Use Gravity" is tagged it seems to be slowed down, or grounded and accelerates very slowly. Why is that exactly? Shouldn't the acceleration of the object moving forward be independent of the gravitational force?

Thanks in advance!

 

Check your physics materials for both the plane and the cube. If you have gravity and mass there will be a force acting downwards. If you have not assigned a physics material to your colliders, then Unity will use the default (I believe it is 0.6, 0.6, 0 bounce, average, average). Your object will be affected by friction. Make your own with all zeros and apply it to both objects.

The rigidbody will also be slowed by any drag values you have set on it. If you set drag to zero and friction to zero, any force that gets it moving will have the body moving for ever.

 

Thanks! That was exactly it. (I only had a physics material on the Rigidbody with friction set to zero.)