Scene one that I looked at was when agent Ethan Hunt has to jump from one building to another in Shanghai to break into a heavily guarded laboratory. Now is this actually possible? To find this out we need the height of the buildings, the distance between them, his initial angle, the amount of time he swings and of course wind and gravity will play a part. The film tells us the first building is 226m and the second building is 162m and the distance between them is 64m. His initial angle is 0 degrees and it took roughly 13 seconds to swing across. Depending on wind speed and direction which is uncontrollable would dictate if he landed on the building over missed it.
The second scene is the impressive bridge jump where Ethan has to jump over a huge gap. To see if this possible we need the angle jumped at, length of the gap, and the speed of Ethan before he jumped. The gap is about 7 meters considering Ethan Hunt is 5'7 and it roughly to be 4 or 5 Ethans across. There is no angle at which he jumped so his height would have to come from the power of his legs. Knowing Ethan to not have a tall frame even if he ran fast enough his body shouldn't be capable of achieving that jump.
Scene three is the helicopter chase in the wind turbines and could Ethan's helicopter go through the turbine without the blade touching the helicopter. We need the speed of the helicopter being tilted at a 45 degree angle, the time it takes for the blade to make a 120 degrees rotation. Wind turbines in which roughly the blades move 120 degrees in roughly 1 second and can travel over 100 mph depending on wind speed. The average helicopter goes 160 mph but in this case tilted it would seem the helicopter would have to hit the blade at some point going through.