'Impossible' rocket drive works and could get to Moon in four hours

[gravityblock]

That is worse than wrong.

Well, if you call the inversion of truth right, then I guess that is worse than wrong for you, LOL.

Woe unto them that call evil good, and good evil; that put darkness for light, and light for darkness; that put bitter for sweet, and sweet for bitter!

Gravock

[MarkE]

Well, if you call the inversion of truth right, then I guess that is worse than wrong for you, LOL.

Woe unto them that call evil good, and good evil; that put darkness for light, and light for darkness; that put bitter for sweet, and sweet for bitter!

Gravock

You are free to try and find any authoritative reference that claims as you do that F=mA is conditional on V <> 0.  Or you can pick-up any physics primer and find that no such restriction is imposed.  If you have any doubts about this: you can sit down and either read or solve the equations of motion for a simple pendulum, or mass / spring combination.

[gravityblock]

You are free to try and find any authoritative reference that claims as you do that F=mA is conditional on V <> 0.  Or you can pick-up any physics primer and find that no such restriction is imposed.  If you have any doubts about this: you can sit down and either read or solve the equations of motion for a simple pendulum, or mass / spring combination.

Like I said, restrictions or no restrictions.......the acceleration is 0, the force is 0, and the velocity is 0.  Either way, it's 0.  It is, what it is!

Gravock

[gravityblock]

@Gravityblock
You are correct because the correct statement is a Net or unbalanced Force is equal to Mass times Acceleration. So yes obviously the Force acting on the mass is the sole cause as to why the mass moves and when the velocity changes we call this an acceleration. If the mass is not moving then there is no acceleration, thus the statement F=mA is false and Net F=mA is true.

AC

F=mA is false and Net F=mA is true  <------ That is an elegant way of writing it!  This is so beautiful!  It's like poetry in motion.

Gravock

[TinselKoala]

Acceleration only applies to moving objects, thus F=mA only applies to moving objects.  However, if you want to apply F=mA to a stationary object (which is absurd), then fine by me.  It doesn't change what it is, and that is an acceleration of 0, a force of 0, and a velocity of 0.  It is what it is!

Gravock

Ah... no.

Gravity is an acceleration, the value of which is 9.8 meters per second per second. You will note that those units are the units of acceleration. A stationary object resting on a scale in a gravitational field, like in your post office, exerts a force downward on the scale, the value of which is F=mA, that is, the downward force on the scale is equal to the mass of the object times the gravitational acceleration in the post office. Everything is stationary, the mass is experiencing a downward acceleration and thus exerts a force (weight) on the scale.

http://physics.ucsd.edu/~tmurphy/phys10/lectures/07_freefall.pdf