These words refer to the energy with which objects are propelled, bear down or collide. Impact is specifically restricted to an emphasis on the moment or point of contact between objects, one or both of which have been in motion: the impact of the meteorite on the earth’s surface; the impact of two speeding cars. In emphasizing the contact itself, the word remains relative about the amount of stress developed: the faint impact of rain on his forehead; the mile-wide crater that would result from the impact and explosion of the bomb. The word is often used metaphorically for any effect: the impact of a tax cut on the economy. Here, again, the word remains relative about the amount of effect engendered. The more formal concussion is closely related to impact in stressing collision, but is even more specific, referring to the considerable destructive energy released, usually with resulting damage of a temporary or permanent nature, as in its reference to brain damage from a blow: suffered a concussion in the car accident that would heave him paralysed for life. Even outside this specific use, it suggests a violent impact : delicate instruments that could not survive the concussion of any hard landing on the moon.

Jolt and shock are more informal than the previous words. They are both more general than but otherwise closely related to concussion in stressing the giving off of considerable energy, as in collision or blow. Jolt may suggest a sudden shaking motion imparted to one body by another that is in motion: thrown back in his seat with a jolt by the sudden slamming on of his brakes. It is widely used in a more general context for any surprising or stunning occurrence: scientific discoveries that came like jolts to awaken the scholastic mind of the era. Shock suggests an abrupt and heavy impact or onslaught: reeling back under the first shock of the attack. But the word’s other meanings are inevitably present as overtones here, implying a numbed unbelieving response or physical collapse from injury: the shock with which she took the tragic news; a blow that sent him into a state of shock .

Brunt suggests an energetic bearing down that may or may not be supportable; once this may have referred particularly to abruptness of contact, much like impact : wiring that could not bear the brunt of any heavy flow of voltage. Now, more often, it refers to a steady demand that taxes endurance: the brunt of so many debts and so little earning power. Force is the most general of these words and may refer to the degree of energy with which objects make contact or to the amount of propulsion with which things move: grenades with enough force to blow up a well-constructed enemy bunker; applying enough force to dislodge the boulder; gamma rays that strike the earth’s atmosphere with considerable force .