The energy needed to get something up to speed is not really relevant to what happens when the thing hits a person unless the person cannot move.
Consider this thought experiment. Take a two ton car with a flat plate on front, accelerate up to say 2 mph, and hit someone.
Now try the same thing but instead of a two ton car lets use a 20 000 ton freight train.
The train takes way more energy to get up to 2 mph. At the time of collision it has 20 000 times as much kinetic energy as the car and 20 000 times as much kinetic energy.
But for the person who gets hit those collisions will be nearly the same. They get accelerated to 2 mph with pretty much the same acceleration profile in both cases. The car is slightly less than the train because the person (especially if they are American!) might be massive enough to cause a slight but noticeable decrease in the car's speed.
Anyone, the key is that the body gets accelerated over a short time to 2 mph. If the body was a rigid body that would involve a very large acceleration for a very short time.
But humans are squishy. The muscles and soft tissue compress and that spreads the time the body takes to reach 2 mph greatly reducing the acceleration, which greatly reduces the damage. The way you get injured in such low speed collisions is by getting knocked over and injured in the fall, or knocked over and run over by whatever hit you, or by being between the colliding object and some immovable object so you can't be accelerated.
Another way to look at that collision is to replace the train with something really big, such as the whole Earth, and instead of accelerating the Earth into the person we'll accelerate the person into the Earth.
That can be done by holding the person horizontally above a solid metal plate and dropping them. If we drop them from 2.69 inches above the plate they well reach 2 mph at the time of collision. You aren't getting bruised ribs from a 2.69 inch fall horizontally onto a metal plate.
Consider this thought experiment. Take a two ton car with a flat plate on front, accelerate up to say 2 mph, and hit someone.
Now try the same thing but instead of a two ton car lets use a 20 000 ton freight train.
The train takes way more energy to get up to 2 mph. At the time of collision it has 20 000 times as much kinetic energy as the car and 20 000 times as much kinetic energy.
But for the person who gets hit those collisions will be nearly the same. They get accelerated to 2 mph with pretty much the same acceleration profile in both cases. The car is slightly less than the train because the person (especially if they are American!) might be massive enough to cause a slight but noticeable decrease in the car's speed.
Anyone, the key is that the body gets accelerated over a short time to 2 mph. If the body was a rigid body that would involve a very large acceleration for a very short time.
But humans are squishy. The muscles and soft tissue compress and that spreads the time the body takes to reach 2 mph greatly reducing the acceleration, which greatly reduces the damage. The way you get injured in such low speed collisions is by getting knocked over and injured in the fall, or knocked over and run over by whatever hit you, or by being between the colliding object and some immovable object so you can't be accelerated.
Another way to look at that collision is to replace the train with something really big, such as the whole Earth, and instead of accelerating the Earth into the person we'll accelerate the person into the Earth.
That can be done by holding the person horizontally above a solid metal plate and dropping them. If we drop them from 2.69 inches above the plate they well reach 2 mph at the time of collision. You aren't getting bruised ribs from a 2.69 inch fall horizontally onto a metal plate.