Monday, May 9, 2011

Two Months in the Temple (Part 1)

The Honors Physics classes are in the midst of an extended project analyzing Indiana Jones and the Temple of Doom's physics: is it real or movie magic?  There's a huge amount of physics here, both obvious (falling rafts, mine car chases, etc.) and implicit (how does that hat stay on his head?, ...just how deep was that pit, anyway?).

They formed themselves into groups, watched the movie, and picked scenes (hopefully, not in that order).

In a change from previous years, I spread out the work: a couple of days here, and a couple there, with longish (a few weeks) breaks in between.  This allows some time for groups whose initial idea didn't pan out to either get it to work or to move on to something else.  I like this model, and I'll use it in the future.

We'll do virtual posters to wrap the project up - stay tuned!

After writing proposals (best proposal gets the scene, if there's a conflict!), the groups have set out upon these quixotic quests (in their own words):

Sweating Bullets

The Scene: Mine cart chase; Indy shoots at the pursuing mine cart

The Question:  A clip in the movie shows two carts moving along the same path. The cart behind the other is rapidly firing bullets at the cart ahead. Both carts continue to move at the same speed. Our group is trying to prove the carts will not be moving the same speed after the force of firing the bullets. After firing 50 bullets, how fast will the cart who fired the bullets be moving? If we assume several of the bullets hit the cart ahead, will that cart increase speed and by how much?

The Game Plan: From the movie we are measuring the initial velocity, final velocity, and number of bullets fired. We will use conservation of momentum to calculate what the actual final velocity is and then we can determine whether or not there was movie magic or it was real phyics. We are using this method because conservation of momentum is good when there are collisions, because there are no net external forces horizontally. The firing of a bullets are like "reverse" collisions.

Bridge Over Troubled Water

The Scene: Rope bridge scene (as it falls after Indy cuts it)

The Question and Game Plan:  We are analyzing the impact received by Indiana Jones when hitting the wall.  We can measure the length of the rope and use this and height to find a final velocity.  Once we have this velocity we can use that and our estimated impact time to calculate the force he receives. We will then determine if this force received is lethal.

Short Round in Dragtown

The Scene: The plane that Indiana Jones, Willy, and Shorty are on malfunctions and is about to crash; they jump out of the crashing plane on an inflatable raft and ride the raft down to the ground.

The Questions:  What is the area of the raft (calculated from the terminal velocity)? Is this area reasonable compared to apparent area of the raft from the video?

The Game Plan: By estimating and measuring the other variables in the terminal velocity equation, we are able to calculate the area.  By finding the terminal velocity using Logger Pro and the video, we will be able to determine if the area of the raft is realistic and accurate according to the calculations.

Whip Swinger

The Scene: Indy swings from one catwalk to the other with a whip during the escape from the mine

The Questions:  What is the greatest net force exerted on the lamp by support Indiana Jones (whip's mass is omitted)?  Also, what is the coefficient of static friction between I. Jone's hand and the whip?

The Game Plan: Using Logger Pro to measure the velocity at the point where the greatest force is exerted (straight down), we can use v^2/r to determine his acceleration. Next we will substitute that into our Fnet equations to find the total force.  For the whip, we will use the same location and velocity to find the coefficient. We will research both the average grip strength of an adult male, and Harrison Ford's mass and height (estimating Indy's grip strength as 3x as strong as an average adult male), and we will use this information to determine the coefficient of static friction.

Out of Sight, Out of Mine