Hello, I've tried solving the following question: A car collides with a tree with a velocity of 75km/h. The car was compressed 1.1m after the collission and the car's mass is 1100kg (including the driver), and the driver's mass is 71kg. a) What is the kinetic energy just before the collission? b) What is the average force that works on the driver during the collission? Now I calculated a) by the regular mv2/2 giving Ek=239 kJ And then b) by v2-v02=2as, where s is the distance 1.1m. Converting 75km/h to 20.833m/s, and setting the equation 20.8332/(2*1.1)=197.29 m/s2, this would then be the constant acceleration. According to F=ma I set the equation: 71kg*197.29=14 kN on average during the collission. Is this calculation correct? I would appreciate some help, thanks!