Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. So, is there anything in the universe will remain at rest forever? It seems NO. Because everything is moving. Any object in outer space remain static? So, how could Newton's first law is valid?
You're kidding right? How could someone who claims to teach "Dynamics, Statics, Mechanics of Solid, Engineering Statistics.", not work this out for themselves? First off, there is no such thing as absolute rest or motion. So you really can only consider "relative rest" or "relative uniform motion". An object can be "at rest" or "in uniform relative motion" relative to something to someone else. Newton's law says that they will remain in that state unless a force acting on one of them changes this. The fact that the pair could be moving or not moving relative to someone or something else is of no consequence. Secondly, There is the "unless acted on by an external force part" Even if everything in the universe is moving relative to everything else, that just means that external forces had acted on them. Thirdly, just because you can't find any instance of objects at rest with respect to each other, or in uniform motion, and entirely free of the influence of external forces, this does not invalidate the First law. It is not making any claim as to how hard it would be to find these exact conditions in the universe.
Well that certainly sounds like a question an engineering professor would ask. Please Register or Log in to view the hidden image!
This started off as ".. will remain in uniform motion in a straight line unless acted upon by an external force." . Newton anticipated Mrs Trellis would write in to point out that a rock at the bottom of her garden hadn't moved since she was born 70 years ago - what did he have to say about that? So he added remain at rest to cover that question before it was asked.
1 N of force is defined as the force that will accelerate a 1kg of mass by 1 m/s^2. But it does not explain what actually is force? Does force exist when there is no acceleration?
This question posed by somebody who claims to teach statics, which is all about force without acceleration. If you're as stupid as you make yourself out to be on this forum, then you're a liar about your employment. If you're not that stupid, then you're a troll, in which case the claimed employment is still probably a lie. As to the question. If there is no acceleration, there is no net force. A spring held compressed by a clamp applies continuous force to the clamp, yet neither object accelerates because the net force is zero. The sum of all the force vectors acting on either object is zero.
A spring compressed in a clamp is isolated from surroundings. A spring compressed in a clamp and taped to the wheel of a moving car is not isolated from surroundings.
Think of a jar of jam sitting on a table. Ask yourself: i) is the jar weightless? ii) Is it accelerating? And then think about what forces apart from its weight are acting on it. Why did you lie about lecturing in mechanics? What was the point of doing that?
Question: A quantity of ideal gas undergoes an expansion that doubles its volume. Does the gas do more work on its surroundings if the expansion is at constant pressure or at constant temperature? (A) constant pressure; (B) constant temperature; (C) the same amount in both cases; (D) not enough information is given to decide. Which answer is correct? A ? Because heat must be added to the system to maintain pressure while the volume expands.
