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Hollywood and Physics

We’ve all seen these kinds of movies. After a fast and dramatic chase, the bad guy jumps out of the car, determined to end the good guy once and for all. His evil plans have been thwarted for the last time! In self-defense, the good guy is forced to take a shot and when the bullet hits, the evildoer is thrown violently backwards as a result of the impact and through the nearest shop window. Once the hero is reunited with the love of his life, the credits roll and we are left to wonder if that’s really how physics work.

In a previous example we calculated the momentum of a common 9 mm bullet (p = 5.4 kg m/s). Suppose the m = 75 kg evildoer gets hit by just this bullet. Since the bullet practically comes to a halt on impact, this momentum has to be transferred to the unlucky antihero for the conservation of momentum to hold true. Accordingly, this is the speed at which the bad guy is thrown back:

5.4 kg m/s = 75 kg ยท v’

v’ โ‰ˆ 0.07 m/s โ‰ˆ 0.26 km/h โ‰ˆ 0.16 mph

This is not even enough to topple a person, let alone make him fly dramatically through the air. From a kinematic point of view, the impact is not noticeable. The same is true for more massive and faster bullets as well as for a series of impacts. The only thing that can make a person fall instantly after getting shot is a sudden drop in blood pressure and the resulting loss of consciousness. But in this case, the evildoer would simply drop where he stands instead of being thrown backwards.

This is not the only example of Hollywood bending the laws of physics. You’ve probably heard the weak “fut” sound a Hollywood gun makes when equipped with a silencer. This way the hero can take out an entire army of bad guys without anyone noticing. But that’s not how pistol silencers work. At best, they can reduce the the sound level to about 120 dB, which is equivalent to what you hear standing near a pneumatic hammer or right in front of the speakers at a rock concert. So unless the hero is up against an army of hearing impaired seniors (which wouldn’t make him that much of a hero), his coming will be noticed.

This was an excerpt from my Kindle book: Physics! In Quantities and Examples

For more interesting physics, check out my Best of Physics selection.

Bankruptcy And Students: Many Students Fail To Pay Off Their Debt

Young people in their early twenties, of which many are students, are becoming a fast-growing number of bankruptcy filers. Bankruptcy and students seems to be becoming a problem, and according to recent surveys, it is believed that teenagers younger than nineteen years of age own at least one credit card of their own. Also, it is reported that two thirds of undergraduate students have a minimum of one open credit card account, and it is believed that the average student graduates owes three to four thousand dollars in credit card debt along with other debts.

Managing Student Finances for the First Time May be a Reason for Defaulting

With more college students being marketed credit cards, it has even made some states enact legislation that limits solicitation to college students and recent bankruptcy reform procedures are also concerned with addressing the problem of bankruptcy and students. The reason behind bankruptcy and students becoming a big problem could lie in the fact that college students are learning to live alone and manage their own money for the first time, and thus find it hard to keep track of their credit card purchases.

According to experts, people tend to shop more with credit cards than when spending cash. When interest, late charges, increase in minimum payments are factored in, it makes for difficulty in managing finances and thus leads to bankruptcy and students becoming a growing malpractice.

Bankruptcy and students loans that are not repaid can often make a student feel as if he or she has just graduated from the school of hard knocks. Bankruptcy is not the escape route that students may be thinking of taking in order to avoid paying back government backed student loans as well as school loans backed by non-profit agencies. These loans are not discharged in a bankruptcy and have to be paid back after bankruptcy, though if a student can prove (very difficult actually) that the loan constitutes a considerable hardship, it can be got rid off without repayment.

Student loans, under normal circumstances, cannot be discharged under any chapter of the Bankruptcy Code. By using loopholes in government legislation, bankruptcy seems to offer an escape route to avoid paying off student loans, and the number of students that used bankruptcy to avoid paying off their debts increased dramatically over the recent past few years.

The bottom line is that it is the bankruptcy judge that has the final say, and for the lucky student, the odd bankruptcy judge may allow him or her to discharge the loan by filing for bankruptcy. Lenders too, cannot send their bills to a student who is in bankruptcy and need to wait till the case is decided. Often, it is better for the student to deal directly with the lender and find a mutually agreeable way of settling the debt, rather than going in for bankruptcy to avoid repayment.