- #1
jguth
i got into a disagreement with someone about how much damage a car would do if it collided with a tree. the other person said that the faster you are going when you hit the tree the more dmage is done to the tree. i replied by saying that at a point the structure of the car yeilds and this is not true. my exact response was :
could someone explain to me if her is right why it doesn't matter if the structure yeilds, or let me know that i am right
thanks
jguth
if you have x amount of energy when you hit a tree the energy has to go into somehting. it can crush the car, break the tree, be dissapated as heat etc... if you hit the tree at a velocity where the energy only involves the frame of the car and the tree then the tree will probably be damaged. however at a high enough velocity the momentum of the engine block will cause it to shear from the body (as it is designed to break off and drop down) and keep going. this will affect the mass of the car. if the frame of the car stays intact all of the energy is dissapated on the tree as the tree must exert that force back. however if you hit the tree with enough velocity that the body deforms and crushes it is a different problem. look at a beer can against your head. if you move the can at a smedium velocity it will hurt like **** and probably cut your head. however, if you provide enough energy into the system by giving the can a higher velocity, there will be enough energy for the structure to yield. when this happens not all of the energy is going into your forehead because some of it is required to cause the can to crush. you are ee, the physics you learned in high school can not explain the new problem of the yeilding object. please to not try to talk about that which you do not know
kthnx
could someone explain to me if her is right why it doesn't matter if the structure yeilds, or let me know that i am right
thanks
jguth