Have you ever been playing a game, or watching an action-adventure movie, and seen the main character throw a knife twenty feet to hit a guy that's about to shoot him? Have you every wondered how much force it would take to hurl the knife that far, and at which angle above the horizontal the knife was thrown from? Well, toady's your lucky day, because this web page shows what physics allows this supposedly realistic game to do.
There are several examples that will be shown to prove whether "Soldier of Fortune" is realistic or not. They are as follows:
1. At what initial velocity will a knife have to be thrown from to go from one side of a room to another?
2. What is the coefficient of friction needed to stay standing on a train when it comes to a sudden stop?
3. What is the momentum of a bullet fired from a shotgun into a wooden chair?
4. Assuming constant force, how far will each gun be thrown when it is dropped (for some reason the guns are thrown instead of just dropped)?
5. Is forward momentum kept when leaping from a speeding object?
1. The following is a picture of the room in question, and the object on the floor is the knife, which weighs in at .46 kg.
Timed with a stopwatch, the knife took .70 seconds to fly the estimated distance of 22 feet. Using the equation s=vt+a(t*t), we can find that the initial upward velocity of the knife is about 6.7m/s, because the position of the knife was 0 at both time t and time 0. We can also tell that the horizontal velocity of the knife was about 9.58m/s. Adding these vectors the total velocity of the knife was 11.69m/s. The direction happens to be 35 degrees above the diagonal.
2. The second example is how the hero (or heroin) of a show is almost impossible to knock off a vehicle, be it car, train, motorcycle, etc. This example is going to show what the coefficient of friction would have to be for our hero to be able to stay on the train when it goes from 19.4m/s to a complete stop, in a very short time period (i.e. negligible). Since our hero doesn't move at all when the train stops, we can ascertain that the force exerted by friction on our hero is infinite (because the time is 0 (in acceleration) gives you an infinite, or undefined, number then friction is also infinite). we guess the programmers didn't consider friction to be very important when making the game...This so far this is the only unrealistic aspect found.
<A train that starts and stops very quickly>
3. The point of this example is to see if momentum is conserved when a gun is fired at a chair, which then goes rolling across the floor. Hopefully, the wheels of the floor and the floor itself have just been waxed and polished, because the surfaces are presumably friction's. The chair itself goes rolling back with a velocity of about .95m/s. The game tells us that the bullet leaves the muzzle at a velocity of 385mps. The bullet weighs maybe 54 grams (This is one of the only things that the game doesn't tell us about weapons), while we can say that the chair weighs about 1kg. This means that the momentum of the bullet was 20.96, and the momentum of the chair with the bullet implanted in it was 4.801. That's way off, and it's obvious that momentum wasn't conserved. This means that in another respect SoF is inaccurate to physics.
<The ill fated chair>
4. In the game there are lots of weapons. we would think that when one runs out of ammo and drops the weapon he wouldn't care how far it goes so he would throw with constant force. So, using the weights the game gives us for the guns we want to know how far each would go when thrown down. The three example guns we am using are the sniper rifle (6.8kg), the shotgun (4.86kg), and the pistol (.86kg). Using the middle one as the test (standard), we will see if how far apart the guns will land. Lets say that the shotgun is thrown with an initial velocity 1m/s. This means that it goes 1.064m (flight time of .65s for all guns). Since force is lessened for greater mass and lessened mass, the guns should land in different places. But, they all landed in the same place. Therefore SoF isn't realistic in that respect.
<All three guns landed in the same place, making the experiment is failed>
5. For this final experiment we will be on a speeding train. we will then jump of the train to see if we travel at the same speed as the train until we hit the ground. If we do, then SoF is realistic. If we don't, then it's not realistic. Below is the picture of the speeding train (Yes, we're cheating so we can get a good picture of it).
Well, it passed the test, we was in the same still moving as fast as the train when we jumped as right before we hit the ground.
In three out of five respects SoF is inaccurate based on physics. But, that's probably better then most games. They might say that SoF is a realistic game, and in some respects it is, but physically it's not something that we would use as an advertising scheme.
Michael Hazlett and Micah Caldwell