Display vectors: Display values:
The units in the animation are MKS (meters, kilograms, and seconds). Each grid space represents two meters. The mass of the object is 1 kg. Click on a point in the animation to display the x and y coordinates. In the vector displays, the vector components are blue arrows, while the resultant vector is displayed in red.
The central mass is an arbitrary large value chosen for convenience. Newton's law is integrated numerically by a Runge-Kutta algorithm. In the numerical displays, the total-energy and angular momentum values are calculated from the instantaneous position and velocity, not from the initial conditions. Therefore, checking that they remain constant is a good crosscheck of the integration accuracy. Note that some initial conditions may give strange results if they result in the object passing too close to the force center. For example, a force exponent of 3 will usually result in a logarithmic spiral into the center, and eventually the integration will fail, resulting in a wild jump across the display. Similarly, starting with zero velocity will result in a fall into the center and eventually a failure of the integration.
By Robert Johnson, using the Physlet Animator and dataGraph classes from Wolfgang Christian and Mario Belloni.