A freely rolling 1200kg car moving at .65m/s is to compress the spring no more than 7 cm beffore stopping. a) what should be the force constant of the spring, and what is the max amount of energy that gets stored in it? b) if the springs that are actually delivered have the proper force constant but can become compressed by only 5 cm, what is the max speed of the given car for which they will provide adequate protection?

Question

A freely rolling 1200kg car moving at .65m/s is to compress the spring no more than 7 cm beffore stopping. a) what should be the force constant of the spring, and what is the max amount of energy that gets stored in it? b) if the springs that are actually delivered have the proper force constant but can become compressed by only 5 cm, what is the max speed  of the given car for which they will provide adequate protection?

anonymous · Answer

$$\Delta(K+U)=0$$
where K is the kinetic energy, and $U=\frac{1}{2}kx^2$ is the potential energy.