Bad Movie Physics Hurt Scientific Understanding

eldavojohn writes "A paper published by UCF researchers claims that bad movie physics hurt students' understanding of real world physics. From the article, "Some people really do believe a bus traveling 70 mph can clear a 50-foot gap in a freeway, as depicted in the movie Speed." The professors published this paper out of fear that society will pay the price. One of the authors commented on advancements in the past years "All the luxuries we have today, the modern conveniences, are a result of the science research that went on in the '60s during the space race. It didn't just happen. It took people doing hard science to do it." I commented on the physics of the most recent Die Hard having problems detracting from my enjoyment of the movie but is it really the root of a growing problem of poor science & math among students?"

Comments

Re:Not yet? Really?

[litghost]

Well this comment shows the problem right away. This is actually a mass independent problem, as gravity is always accelerating things (on Earth) at ~9.81 m/s^2. The problem is more what the drag on the bus is over the course of the flight. However, since I am not in the mood to calculate Reynolds numbers for flying busses, I will assume inviscid air.

Problem statement: A point particle moving at 70 MPH at some angle must cross a 50 foot gap, and be at the same height when it reaches the other side.

Given:
v0 = 70 mph // Initial speed
x = 50 feet // Distance to travel horizontially

Assumption: Force-free motion
Constant gravity ( g = 9.81 m/s^2 )

Solution:

v0 = 70 mph = 31.2928 m/s
x = 50 feet = 15.24 m

t = Time of flight
theta = Angle from horizon

x = v0*t*cos(theta)
y = v0*sin(theta)*t - g*t^2
Solve for t t = x/(v0*cos(theta))
Substitude into y equation
y = x*v0/v0*sin(theta)/cos(theta) - g*x^2/v0^2/cos(theta)^2
Set y = 0 and solve
x*sin(theta)/cos(theta) = g*x^2/v0^2/cos(theta)^2
sin(theta)*cos(theta) = g*x/v0^2

g*x/v0^2 = 9.81*15.24/(31.2928)^2 = 0.15267

sin(theta)*cos(theta) = 0.15267 can be solve graphically. The first valid solution is 8.89 degrees.

So yes, a bus (with no friction) can cross a 50 feet gap, if the ramp was at an incline greater than 8.89 degrees.

Yay.

Re:I like how people complain about that bus jump.

[eldavojohn]

They had to used CGI to edit the landing area shorter, to make it look like it landed closer to the edge than it actually did, because the bus actually jumped farther than it should have. (And they edited out the camera rig it smashed into.) Um, there was no gap. The gap was edited in. In all sources I've found, they even talk about the ramp.

According to Wikipedia, you don't know what you're talking about:

Notes

One of the most famous scenes in the film shows the bus jumping across a gap in an elevated freeway-to-freeway ramp while still under construction. Both sides of the gap are at identical heights, making it impossible that the jump would work in real life. According to the "Making of..." feature that accompanied the DVD release, the stunt used a ramp and really did traverse fifty feet in the air. To handle the sudden jolt on landing, the stunt bus had no passengers aboard and the driver was wearing a shock-absorbing harness.

The gap in the highway was added through CGI; note the flock of digital seagulls added by the special effects company to enhance the realism of the scene. While the flyover ramp is shown to be essentially all complete and paved, except for the gap, in actual construction that gap in the road deck would have been fixed before the guardrail and asphalt is added. You may also note if you look closely, when the bus is flying over the bridge that is under construction the gap between the two bridges was edited in. And IMDB.com seems to agree:

The bus jump scene was done twice, as the bus landed too smoothly the first time. The bridge was actually there, but erased digitally. So you seem to have your facts wrong there. Please cite your source, I would find this interesting as I've always heard the above.

You should really write the authors of that paper though, I think they'd get a kick out of your comments and they'd love to add you as a data point.