So first off, we need to remember that Tom Cruise is only 5'7". This will give us an idea of the actual size of the "Stunt Scenes".

The Building Fulcrum

Ethan Hunts teammates kindly give us the information needed to confirm the fulcrum. The first building is 226 meters tall, the second building is 162 meters tall, and the distance between is 47.55 meters. Although he does run off the side of the building, his running speed is irrelevant since it would be considered a factor on a Z-axis which is not required for a situation of this kind. It would be relevant if you were attempting to pinpoint his landing on the roof. His initial decent on the Y-axis would have been 0 m/s because he was stationary until gravity (-9.8 m/s) took effect as he began his free fall from the top of the building. His initial and final Y-axis velocity would have been 0 m/s as the fulcrum starts from a stationary point on the roof of the first building and ends as he detaches the cable from himself at the top of the second building. Unfortunately we do not know the weight of Ethan Hunt which could help us find the velocity while he was at the bottom of the fulcrum which could prove whether he would have made it up to the top of the second building.

The Fulcrum Drop

After the infamous fulcrum that Ethan Hunt engages and completes successfully, he dropped after detaching the cable. As he detached the cable he had a Y-Axis velocity of 0 m/s. Gravity's effect on Earth is -9.8 m/s^2. He dropped for approximately 3 seconds before hitting the roof. Using the formula Vf=g*t we can find his velocity when he hit the window on the slanted roof. This formula yields a final velocity of 29.4 m/s (65.77 mph). If a human being hit a still object at 65.77 mph without any major protection (helmet) there would be serious injuries or death. Ethan Hunt simply grunts and seems to walk it off which I rule impossible.

Car Slide

After the bridge fight scene, Ethan Hunt jumps in a convertible to attempt to save his wife. During this scene he is in a convertible while speeding and swerving through traffic. At one point he is headed directly towards a semi and pulls the e-brake and fishtails to his left. Notice I said E-BRAKE. After he does this, the camera view switches and he is immediately going a velocity near his initial before applying the brake. Brakes are designed to slow you down significantly, and turning a car sideways while having the rear brakes locked would result in an incredible deceleration. While this is being said, the car would need a motor much larger and more powerful then a stock convertible to be able to get to a velocity in under one second after such a large deceleration. Even modern drift cars and super cars are unable to accelerate that fast after being slowed down. I call this scene impossible due to the car's velocity directly after a deceleration of that scale. Unfortunately I cannot remember any quantities from this scene, but from pure eye-sight it seemed the car was traveling around 50 mph when it entered the slide and was in some way able to exit the slide doing around 50 mph.

I would have liked to see more focus on actually estimating the quantities needed to answer your questions. That was, after all, the point of the exercise. Particularly for the car slide scene, you only gave very rough estimates of two quantities.

ReplyDeleteIncidentally, you might be interested to know that what really matters in the fulcrum scene is how far he is able to get himself away from the building he is aiming for. A pendulum swings equally far on either side of its pivot point, so he would need to get just as far to the one side as he wants to swing on the other side. This is why he jumps off the building heading the opposite direction of where he ultimately wants to go. So his speed is going to be extremely relevant. If he can’t get far enough out to the one side, then he has no hope of reaching the building when the pendulum swings across.