But I am going to go with a constant force of about 3 Newtons. Remember that I have assumed the frictional force is constant and in the opposite direction as the velocity. Now I can solve for the frictional force: That means that the decrease in kinetic energy will be due to the work done by friction (friction will do negative work since it is pushing in the opposite direction that the bird is moving). If it is at the same location, it will have the same gravitational potential energy. For one bird, there is a case where it just about gets back to the same location, but at a slower speed. If this is true, then I can look at one rotation of the bird around the rock. So, let me assume that this frictional force is in the opposite direction as the velocity of the bird. If that is the case, at some instant I could draw the following forces on the space bird. What if there is some constant frictional force that is in the opposite direction as the motion. What to do now? I guess I need some estimate for the frictional force on the bird. If there wasn't a frictional force, I could just use the kinetic-position graph to find a function to add to that such that the total energy would be constant.
#Angry birds space plus#
This means the kinetic plus potential energy of the system is not constant. Otherwise when the bird gets back to the same altitude that it started at, it would have the same speed (and same kinetic energy). How can this be? My first guess is that there is some type of friction involved. The bird can be at a certain distance from rock and have more than one velocity. I put a line to mark the location that the gravity starts to act on the bird (should I even call it gravity yet?) Also, there is another problem. If you want to think about the way the bird moves, in this graph it would start at a high r value and move left in the graph (to a lower r value). The horizontal axis is not time (I know I already said that). Here is a plot of the kinetic energy as a function of distance from the center of the rock.Ī couple of things to notice. A small error in the position data can make a huge error in the kinetic energy since it depends on the square of the velocity.īut like I said before, I don't really care about time data. Why? Well, I suspect there are some slight frame rate problems with my screen capture.
Before that, the kinetic energy SHOULD be constant – but there are some spikes in the data. I added the red arrow to indicate the location on the graph where the bird entered the "sphere of gravity". If I assume a bird mass of 1 unit (call it kg if you like) and a scale where the sling shot is 4.9 meters tall (from the Angry Birds Terrestrial game) then this would be a plot of kinetic energy vs.
#Angry birds space free#
How? First, get some screen captures of motions in the game (using the desktop version of the game) and then use the free (and awesome) video analysis program Tracker. I can't directly measure the potential energy for this system. Please don't confuse momentum with the CHANGE in momentum. In fact, for circular motion the force and the momentum are NOT in the same direction. Although the change in momentum is in the same direction as the force, the momentum might not be. This might seem like a great way to go, but the problem is that both the force and the momentum are vectors. In the momentum principle, I can find the forces on the bird (probably just the gravitational force) and in a short time interval, I can write: When dealing with orbits, it is easier to use the Work-Energy principle than it will be to use the momentum principle. That is not a perfectly circular orbit, but it will work. What if I shot a bird (not shot THE BIRD) in such a way that it sort of went around the asteroid, like this: But how could I test if this is indeed the way gravity works in Angry Birds Space? Honestly, I think the best thing is to look at orbital motion. Here, G is the gravitational constant the m's are the masses of the two objects and r is the distance between their centers.
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