Why do ships shake when something hits their shields?

Question

Why do ships covered with energy shields shake when these shields are hit with a pure-energy weapon? Shouldn't pure-energy shields completely absorb a pure-energy blast? Not to mention any idea of reusing / recycling / recuperating that hit's energy to strengthen themselves.

Is the explanation:

• out-of-universe: makes the scene more dramatic/intense,
• in-universe: to let characters know, that they're actually in trouble (like a stick-shaker, letting the pilot know the plane is in trouble),
• any other (like a technical one)?

This is tagged to be a Star Trek-specific question, because it came to my mind, when watching a DS9 episode. But could actually by asked about any SF work that involves energy shields and energy weapons hitting them.

Answer 1

The answer can be found in this question. The Structural Integrity Field fluctuates as power is drawn to the shields.

The structural integrity field (abbreviated SIF) was a technology developed by spacefaring cultures to supplement the natural structural integrity of the material their starship hulls or other constructions were composed of. Engineers used a structural integrity force field to supplement the supports and bulkheads that gave a piece of architecture its shape. This technology was made necessary by the fantastic stresses and probability of a hull breach presented by warp fields and spatial phenomena present in the galaxy.^source

Examples:

In order to stop the USS Defiant from being torn to pieces by exceeding warp nine in 2374, Chief Miles O'Brien took power from the phaser reserves to strengthen the starship's structural integrity field. (DS9: "The Sound of Her Voice") In an alternate timeline in 2374, the USS Voyager was forced to engage warp drive while the structural integrity field was still down, in order to escape the Krenim weapon ship. As a result, many of the outer hull plates were torn from the ship. (VOY: "Year of Hell") The warp coils of an Intrepid-class starship would rupture within a short time if the structural integrity field around them collapsed.^source

^source

Answer 2

In the Hospital Station stories by James White there were weapons called rattlers which used rapidly alternating tractor and pressor beams to shake enemy spaceships to pieces.

I once read about designs for laser weapons which would not vaporize what they hit but would rapidly alternate from on to off to on to off to on...and eventually smash their targets with a series of repeated blows.

So maybe phaser beams are designed to make enemy space ships shake to pieces if their structural integrity fields are not strong enough.

Perhaps if a phaser beam hits a force shield it will be stopped and not hit and vaporize its target, but it will transfer its kinetic energy to the force shield which will be pushed backwards and transfer that energy to the force field generators which will be pushed backwards and transfer that energy to the entire ship they are mounted on which will be pushed backwards a little and seem to shake. Some parts of the spaceship might be pushed back more than others and the spaceship might deform very slightly and then rebound which may create a shake.