Are you smarter than a freshman? There are probably more than a few college graduates on Auburn’s campus, especially those of us in engineering, who often ask themselves this question. Try your hand at this freshman physics problem and find out for yourself.
Question: A small object of mass m = 0.4 kg is traveling along a horizontal surface. The only horizontal force acting on the object is a resistive drag force proportional to the speed of the object such that FD = - c V where FD is the drag force, V is the speed, and c is the coefficient of proportionality such that c = 8 kg/s. The object passes point P with a speed Vo equal to 2 m/s. How far beyond the point P does the object travel before it comes to rest?
Answer:
The acceleration of the object is proportional
to the net force such that:
m a = FD = - c V
In this case, we want to find the speed,
m dV = - c dX
L = Vo m = 2 m/s . 0.4 kg = 0.1 m c 8 kg/s
V , as a function of position, X . Thus,
the acceleration is given by:
a = dV = dV dX = V dV dt dX dt dX
Thus:
- Vo = - c L m
This launcher has seen a great deal of action in the Gulf War theater and the conflicts in Iraq and Afghanistan. “Even in nontraditional conditions, this missile still does what it needs to do,” says Zieman. “The technology behind it is incredible.”
m a = m V dV = - c V dX
∆V = -c ∆X m
Don’t let the hunk of metal fool you. Inside the launcher are circuits and computer cards and internal sensors. There are probes that “talk” and built-in tests that allow the launcher to check itself and transfer information to the pilot. A launcher must have a remarkable degree of compatibility with its missile. As one of the smaller guided missiles, the HELLFIRE continues to be refined to enhance performance characteristics and decrease the possibility of collateral damage.
Auburn Engineering 13