How to make an animation so that it is smooth and plays at one speed?

I tried different settings, but I haven't received the desired result. Either the animation is smooth but first it slow then speeds up and then slows down at the end (Bezier) or animation rude but it has one speed (Linear).
Example:

Is there a way to make the animation smooth and have it play with one speed without acceleration & deceleration?

The image above is the simplest way to visualize what i mean, but the image in this link shows the kind of objects i'm animating, and it behaves quite abrupt when Linear, but Bezier gives pronounced easing in-out:

• All lifelike animation is done using Arcs, and a bit of easing in and out replicates the Inertia experienced in real world objects. Here are the 12 principles of animation, to reiterate – zeffii Jun 13 '15 at 12:08
• While different interpolations make simple animations easy, when you get into more complex animations like characters, you should expect to set a keyframe nearly every frame for key parts of the armature. – sambler Jun 14 '15 at 11:31
• Due to the acceleration and deceleration the animation looks bad and than more intermediate frames than animation looks worse. That is why I would like to know how to make a smooth animation without changing the speed. – Juliya Jun 14 '15 at 17:09

Then Add a Follow Path constraint, and press Animate Path, then press Play to see what that looks like.