Question

Two students are studying for their upcoming physics exam and discussing the differences between directed motion and random motion. While reviewing the students make the following comments:

Kenny: Directed motion and random motion are two separate things. In directed motion you can use Newton’s Laws to describe the motion of individual objects, but when objects exhibit random motion they are equally likely to move in any direction. For Newton’s laws to apply there must be net movement in a particular direction.

Jesse: I thought that the difference between random motion and directed motion was just a matter of how closely you examine what’s going on. Newton’s Laws still apply for objects undergoing random motion, but it would be really hard to work out all the details.

React to each student’s statement and discuss what you think about random motion. Do Newton’s Laws apply? Can you reconcile Kenny and Jesse’s statements? Note: This is an essay question. Your answer will be judged not solely on its correctness, but for its depth, coherence, and clarity.

Answer 1

1>

The main features of using Newton laws of motion are , if we know the current position and velocity of the particle then we can certainly say what will be it's future position , momentum etc with respect to rate of change of time .

2> Here Kenny and Jesse both are right .

According to kenny For Newton’s laws to apply there must be net movement in a particular direction. Particle follow net result .

And also

According to Jesse  thought that the difference between random motion and directed motion was just a matter of how Closely you examine what’s going on.

3>

It's is matter of how Closely we can examine net effect within very short interval of time because laws are still same . They completely applicable to random motion also . In physics we deal some kind of nonlinear problem in chaos theory.

4> ( little extra information for to be aware of scale of use )

But these all only applicable under classical world where Newton laws are applicable but as we go to nano scale we are no more allowed to use Newton laws where Heisenberg uncertainty applied. So the scale at which we are performing experiment it's important.