In a forward collision, the driver and everyone else's head is thrusted back (because the energy transfer from one car to another [i.e. the Inertia] ).. the head rest is there to stop the heads from moving to far back that it could break your neck.
Answer:
If the volume of a gas increased from 2 to 6 L while the temperature was held constant, <u><em>the pressure of the gas decreased by a factor of 3.</em></u>
Explanation:
Boyle's law that says "The volume occupied by a given gaseous mass at constant temperature is inversely proportional to pressure." This means that if the pressure increases, the volume decreases, while if the pressure decreases, the volume increases.
Boyle's law is expressed mathematically as:
Pressure * Volume = constant
or
P * V = k
To obtain the proportionality factor k you must make the quotient:

k= 3
This means that <u><em>if the volume of a gas increased from 2 to 6 L while the temperature was held constant, the pressure of the gas decreased by a factor of 3.</em></u>
Spinning top, moving car, and rolling ball have kinetic energy I believe