I would say the last one but I’m not sure if I’m directly correct ..
Answer:
Given: Vi = 382 km/h, Vf = 0 km/h, Mc = 705 kg, Md = 65 kg, Δt = 12
Required: Δx
F = Δp / Δt
= ![\frac{(Mc+Md)Vf-(Mc+Md)Vi}{t} \\\\= 6.81 * 10x^{3} N [left]\\\\x=\frac{1}{2} (Vi+Vf)\\ \\ = 637m[right]](https://tex.z-dn.net/?f=%5Cfrac%7B%28Mc%2BMd%29Vf-%28Mc%2BMd%29Vi%7D%7Bt%7D%20%5C%5C%5C%5C%3D%206.81%20%2A%2010x%5E%7B3%7D%20N%20%5Bleft%5D%5C%5C%5C%5Cx%3D%5Cfrac%7B1%7D%7B2%7D%20%28Vi%2BVf%29%5C%5C%20%5C%5C%20%3D%20637m%5Bright%5D)
Mechanical energy is conserved when there are no non-conservative forces acting on the body. Examples are friction and elastic forces of stress in a body. These non-conservative forces convert mechanical energy to other forms of energy like heat and sound
Hope this makes sense