Quote:
Originally Posted by Arctic Fox
don't forget that we are dealing with energy here, not momentum
momentum is mass x velocity: m x v
kinetic energy is "half m v squared": 0.5 x m x v x v
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so, a cart of mass 1 going at speed 20 hitting a brick wall dissipates kinetic energy of 0.5 x 1 x 20 x 20 = 200 units
whereas a cart of mass 1 going at 40 hitting a brick wall dissipates kinetic energy of 0.5 x 1 x 40 x 40 = 800 units
double the speed, and you quadruple the kinetic energy because of the squaring
assuming the two carts are of equal mass and hit head on, the combined dissipated kinetic energy is 200 + 200 = 400 units
it does not matter whether a cart hits another cart head on or a wall - if it is brought to an immediate stop then the kinetic energy dissipated per cart is the same (200 units)
so two carts hitting each other head on, each doing 20, dissipates only half the kinetic energy (400 units) of one cart hitting a wall at 40 (800 units)