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Digital Debunking: Christmas Movie Edition

The holiday season is upon us and magic is in the air. Many of us spend the winter months watching our favorite holiday movies over and over again. This got us thinking about a few classic movie scenes and whether real-world physics would hold up against Hollywood fantasy. We decided to dive into two of our favorites to assess if they pass our credibility test – National Lampoon’s Christmas Vacation and Home Alone.

National Lampoon’s Christmas Vacation

Using Clark’s “non caloric silicon-based kitchen lubricant” on the bottom of your sled will increase your speed and create enough friction to light a trail of fire in your wake.

In the 1989 holiday classic National Lampoon’s Christmas Vacation, Clark Griswold attempts to impress his family by using his company’s new cooking lubricant on the bottom of his sled to drastically increase his speed and achieve a new “amateur recreational saucer sled land-speed record.” To Clark’s surprise, this does not go the way he planned. His efforts to improve speed not only send him shooting down the hill like a rocket, but ignite a trail of fire behind him. Onlookers proceed to watch Clark race down the hill and across a busy road, narrowly dodging traffic before finally crashing into a Wal-Mart parking lot.

With the help of Altair Inspire™, we simulated Clark’s take-off to test if his kitchen lubricant would increase his speed and set fire to the trail behind him. To recreate this, a few assumptions had to be made based on observations of the scene:

  • The snow was dry based on the trail of powder left behind him
  • Temperature was 0° C or below based on how people were dressed
  • The coefficient of friction of a waxed ski on dry snow at 0° C is 0.2 (spray oil can be used in a pinch if wax is not available, so kitchen oil was assumed to be about the same as wax)
  • Clark states that the kitchen lubricant he uses creates a surface “500 times more slippery than any cooking oil”

From this evidence, we calculated that the coefficient of friction for a lubricated sled on dry snow at 0°C was .0004 (0.2/500). With existing CAD of a dummy imported, a hill and sled replica were made to test Clark’s saucer sled fiasco.

Shown above is Clark’s sled compared to a sled with normal friction.

Clark’s kitchen lubricant made his sled travel two times faster than the control sled, but it did not come close to creating enough friction to light a trail of fire. If you happen to get your hands on some of Clark’s special kitchen grease to go for your own sled record, be sure to safely assess your surroundings. You won’t need a fire-retardant snowsuit, but a helmet might not be a bad idea.

Home Alone

Swinging a paint can from the top of the stairs into someone’s head will create enough force to knock them off their feet.

Christmas in the U.S. wouldn’t be the same without the 1990 film Home Alone. As the McCallister family travels to Paris for the holiday, eight-year-old Kevin is mistakenly left behind. Once Kevin realizes he is alone, he watches gangster movies, eats ice cream for dinner, and shoots his brother’s BB gun in the house.

While alone, two thieves named Harry and Marv case the McCallister house. Kevin is startled, but manages to scare them off by thinking on his feet. Overhearing their conversation, Kevin learns that the “wet bandits” are planning to rob his house on the night of Christmas Eve. As the protector of the house, Kevin gets to work creating booby traps to ward off the burglars.

In a famous scene, Harry and Marv chase Kevin up the home’s main staircase. Once at the top landing, Kevin tosses a paint can attached to a rope at Harry and Marv. This knocks Harry off his feet and sends him careening down the stairs, then Kevin tosses another can knocking Marv down to meet Harry.

Thinking about this logically, we wondered if it was possible to knock someone clear off the stairs with the force created by the swinging paint can. Using Inspire, we tested the force created by a 9-pound paint can making impact with someone’s face.

Shown above is the simulated force of a paint can hitting a subject.

Not only does the can knock our test subject off their feet, but it sends them toppling down the stairs to meet the floor. The paint can crashes into our test subject with an incredible 611 pounds of force. According to an article in the Washington City Paper, this is nearly equivalent to the force needed for a martial arts artist to break through a concrete slab 1.5 inches thick.

Thanks to this simulation, we can definitively conclude that being hit with 611 pounds of paint can force would not end well for any would-be bandits.

Thanks for reading and “Merry Christmas, ya filthy animal.”