Spoiler Alert: If you haven’t seen The Amazing Spider-Man 2, or aren’t familiar with the comics, read at your own risk.
Up until The Amazing Spider-Man franchise, Spidey’s girlfriend in the movies and the cartoons was Mary Jane, and Gwen Stacy was never mentioned. If you’ve ever wondered why, you got your answer at the end of “The Amazing Spider-Man 2.” Gwen died during a battle between Spider-Man and Green Hoblin. Although Spider-Man claims Goblin “killed the woman [he] loved,” it is actually Spidey himself who caused Gwen’s death. Here is a physical explanation:
In physics, impulse is the change in momentum and expressed as follows:
F • t = m • Δv
We can use it to estimate the force Gwen experiences when she is suddenly stopped either by hitting the ground or by Spider-Man’s web. Since Emma Stone is 52 kg, we’ll take it as Gwen’s mass. Let’s say the time the force is applied for 0.1 seconds. Now all we need is the change in her velocity. Gwen falls from the George Washington Bridge, which has a height of 184. For the sake of simplicity, we will assume that g (gravitational constant) is 10m/s^2. Using
Vf^2=Vi^2 + 2ad
the final velocity of Gwen is found to be 60m/s. It is also the change in her velocity when Spider-Man stops her with his web. Putting this all in the initial equation, the force Spidey’s web apply on Gwen is nearly 30,000N. For comparison our bones can withstand up to 4000N. So in Gwen’s instance the only way Spidey could save Gwen, would have been shooting a large web and using it as a life net in order to increase the time the force is applied.
Here is the scene from the movie. It’s a little ambiguous whether she hits the ground or not, but there is a clear snap sound that would imply that.