Why does a phone book not leave a bruise when using it with a punch?

Answer 1

The impact is spread out over a larger area

Any impact to soft tissue will leave a mark of some sort, in this case it wont look like a fist but a large flat bruise.

It is for the most part a movie myth used in cases where the police want to rough up a suspect but not leave incriminating marks, and only a myth.

There is no way to issue a beating without leaving signs of that beating, forecsic science has progressed to the point that they can figure out exactly what was used.

Assault is a serious crime, it is a felony and therefore carries a mandatory jail sentence so live and let live.

Answer 2

the phonebook was used as a torture method. they would use the phonebook to strike the victims head. the strike would compress the cervical spine to cause pain. this torture method does not leave any marks and yes, police officers have used this torture method.

Answer 3

it depends not only on the thickness of the phone book, but also on the person's skin turgor, how easily the person bruises, their intake of folate, iron and such minerals. Normal people though, to answer your question, would not bruise.

Answer 4

only if your hit with them

Answer 5

Also, to update my 'conservation of momentum' answer just given, be aware the other posted answer is way off track with this nonsense about the impact being "spread out over a larger area..." This shows a poor grasp of physics. Making sure the phone book is tight against the skin will reduce bruising irrespective of surface area. The point us to mimic the billiard ball or the balls in the Newton ball pendulum: there has to be a continuous matrix of SOLID material -- ie. no air gaps! -- between the striking object (bat, baton, fist) and the subject's body. An air gap would present a huge change in density and materials from the flesh/blood/water matrix found within a human body, and this would hugely affect the transfer of momentum, likely causing skin bruising. A phone book directly against the skin with no shirt in between (or at least ensuring a thin or wet shirt) would work best.

Answer 6

Also, this is NOT a Hollywood myth. It is as real as a Newton ball pendulum or a billiard table, with exactly the same physics as I described below. Some people may have moral qualms about imagining this scenario, but calling it a myth is not an answer when the physics is clear -- physics that does not differ between human and nonhuman examples.

Answer 7

Completely wrong explanation above. If you clobber somebody with a phone book, they will bruise. But there is another way, and it involves knowing a little physics.

Have you ever seen a Newton ball pendulum? It's a desk toy with 5 stainless steel balls. Notice how only the balls on the ends move. The centre balls stay stationary, but they transfer the MOMENTUM from the first ball to the last ball. In physics this is called CONSERVATION OF LINEAR MOMENTUM and it's exactly what happens when you 'break' the billiard balls in a game of pool. The cue ball literally stops, and transfers its momentum to the ball that it has collided with.

Now, what about the phone book? The phone book plays the same role as the middle balls in the Newton pendulum: it doesn't move, but it DOES transfer momentum. If the phone book is firmly pressed against a subject's body and struck with a fist, baton, or bat, the momentum will be transferred deep into the body, causing pain. In some cases the momentum can travel through the body and cause pain/damage far from the original area of impact. But because there is no open gap between the phone book and the skin, there is no 'impact' there, and thus no bruising. Bruising is minimized by making sure the book stays firmly against the skin. Just like a Newton pendulum, just like in billiards.