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# Careers: Physics/The theory of the acceleration of moving objects

Question
In the March 2010 edition of Popular Mechanics; faster, lighter, Space Engines on page 20; Marc Millis, a propulsion physicist at NASA said that there might be a breakthrough other folks aren't even looking for. I think I might have found something. It's called, " The acceleration of moving objects." If an object is moving on a track, and the track is being accelerated at the same time, it would take more force to accelerate the track. If this is true, then what ever the track accelerated from would go backward with a greater force then if the object was standing still on the track. And when the track is decelerated in relation to the object that it accelerated from , there is more force left over in one direction. All that is left is to return the object back to the beginning of the track and start again. Of course the force used to accelerate the object on the track in the beginning and decelerate the object at the end would cancel each other out. It is like pushing and pulling your self through space. It does not go against Newtons laws of motion since the mass of an object increases when it's speed increases which Einstein proved. It would be like accelerating an object through a greater distance in space in the same amount of time which would take more force. Another example would be a long truck that has a safe in the back. As the truck starts accelerating from 0 to 60 MPH , the safe is moved from the back to the front at a constant speed. Would it take more force to accelerate the truck if the safe were moving? One possible way to prove this would be to shake a hydraulic cylinder back and forth while the cylinder is extended out at the same time. My question is would this work as an engine in space? I look forward to your responce. Maybe our flying cars are not impossible after all. My address in  Richard William McCauley.  402 County Rte. 64.  Shushan, New York. 12873.   My Tel. # is. .

Your description is a bit vague and you will find that if you write it down accurately and recast it in terms of free body diagrams, that there is no effect such as you postulate.  Newtonian mechanics works extremely well until you get to relativistic speeds and that means that the concept of "excess force" is not meaningful.  Net forces cause acceleration and the work done by a force is the integral of the force over the path on which it acts.  Forces cannot do more work that this and in fact, they usually do less because of frictional losses.

Careers: Physics

Volunteer

#### Carlo Segre

##### Experience

Professor of physics for 30 years at Illinois Institute of Technology. Academic adviser for undergraduates and graduate students. I have served on university promotion and tenure committees, search committees for Deans and Department Chairs. I have also been an Associate Department Chair and an Associate Dean. I have 34 years experience in materials science research and I have been responsible for building and now managing a User facility at the Advanced Photon Source.

Organizations
American Physical Society
Sigma Xi
American Chemical Society
American Associate for the Advancement of Science
International Centre for Diffraction Data (Fellow)
International X-ray Absorption Society

Publications
Nature; Physical Review Letters; Physical Review; Applied Physics Letters; Journal of Physical Chemistry; Journal of Magnetism and Magnetic Materials; Physical Chemistry Chemical Physics; Solid State Communications; Physics Letters; Journal of Low Temperature Physics; Journal of Crystal Growth and Design; Physics Letters; Journal of Applied Physics; Journal of Archaeological Science; Physica C; Corrosion Science; Electrochimica Acta; Journal of Nuclear Materials

Education/Credentials
Ph.D. Physics, 1981 - University of California, San Diego
M.S. Physics, 1977 - University of California, San Diego
B.S. Physics, 1976 - University of illinois, Champaign-Urbana
B.S. Chemistry 1976 - University of illinois, Champaign-Urbana

Awards and Honors
Duchossois Leadership Professor of Physics, IIT Fellow, International Center for Diffraction Data