To reduce the internal energy U of an ideal gas you need the gas to lose heat and/or do work.
Acceleration is the speed of an object speeding up
Whether it is velocity or just speed
Rate of change of momentum = impact force
(m*v-m*u)/t = F
4000*20/t = 80000 (note: v is zero as it stopped)
<span>soo, t = 1 sec</span>
