Examples of conservative force in the following topics:
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- A conservative force is dependent only on the position of the object.
- Gravity and spring forces are examples of conservative forces.
- We can extend this observation to other conservative force systems as well.
- The total work by the conservative force for the round trip is zero:
- For a conservative force, work done via different path is the same.
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- In any real situation, frictional forces and other non-conservative forces are always present, but in many cases their effects on the system are so small that the principle of conservation of mechanical energy can be used as a fair approximation.
- Let us consider what form the work-energy theorem takes when only conservative forces are involved (leading us to the conservation of energy principle).
- If only conservative forces act, then Wnet=Wc, where Wc is the total work done by all conservative forces.
- Now, if the conservative force, such as the gravitational force or a spring force, does work, the system loses potential energy (PE).
- This equation is a form of the work-energy theorem for conservative forces; it is known as the conservation of mechanical energy principle.
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- Examine all the forces involved and determine whether you know or are given the potential energy from the work done by the forces.
- If you know the potential energies ($PE$) for the forces that enter into the problem, then forces are all conservative, and you can apply conservation of mechanical energy simply in terms of potential and kinetic energy.
- If you know the potential energy for only some of the forces, then the conservation of energy law in its most general form must be used:
- where $OE$ stand for all other energies, and $W_{nc}$ stands for work done by non-conservative forces.
- Do not calculate $W_c$, the work done by conservative forces; it is already incorporated in the $PE$ terms.
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- In the presence of dissipative forces, total mechanical energy changes by exactly the amount of work done by nonconservative forces (Wc).
- We have seen a problem-solving strategy with the conservation of energy in the previous section.
- Here we will adopt the strategy for problems with dissipative forces.
- Therefore, using the new energy conservation relationship, we can apply the same problem-solving strategy as with the case of conservative forces.
- Express the energy conservation relationship that can be applied to solve problems with dissipative forces
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- These examples have the hallmarks of a conservation law.
- The conserved quantity we are investigating is called angular momentum.
- Just as linear momentum is conserved when there is no net external forces, angular momentum is constant or conserved when the net torque is zero.
- This is an expression for the law of conservation of angular momentum.
- Conservation of angular momentum is one of the key conservation laws in physics, along with the conservation laws for energy and (linear) momentum.
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- Mechanical work done by an external force to produce motional EMF is converted to heat energy; energy is conserved in the process.
- As the rod moves and carries current i, it will feel the Lorentz force
- Energy is conserved in the process.
- We learned in the Atom "Faraday's Law of Induction and Lenz' Law" that Lenz' law is a manifestation of the conservation of energy.
- Apply the law of conservation of energy to describe the production motional electromotive force with mechanical work
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- Energy is conserved in rotational motion just as in translational motion.
- The simplest rotational situation is one in which the net force is exerted perpendicular to the radius of a disc and remains perpendicular as the disc starts to rotate.
- The force is parallel to the displacement, and so the net work (W) done is the product of the force (F) and the radius (r) of the disc (this is otherwise known as torque(τ)) times the angle (θ) of rotation:
- Just as in translational motion (where kinetic energy equals 1/2mv2 where m is mass and v is velocity), energy is conserved in rotational motion.
- Conclude the interchangeability of force and radius with torque and angle of rotation in determining force
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- Linear momentum is particularly important because it is a conserved quantity, meaning that in a closed system (without any external forces) its total linear momentum cannot change.
- Momentum, like energy, is important because it is conserved.
- As we will discuss in the next concept (on Momentum, Force, and Newton's Second Law), in classical mechanics, conservation of linear momentum is implied by Newton's laws.
- Only a few physical quantities are conserved in nature.
- Total momentum of the system (or Cradle) is conserved.
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- External forces: forces caused by external agent outside of the system.
- (Gravity and normal force on each puck have the same magnitude, but are in the opposite directions) Therefore, we conclude that the total momentum of the two pucks should be a conserved quantity.
- Without knowing anything about the internal forces (frictional forces during contact), we learned that the total momentum of the system is a conserved quantity (p1 and p2 are momentum vectors of the pucks. ) In fact, this relation holds true both in elastic or inelastic collisions.
- Whether the total kinetic energy of the pucks is conserved or not, total momentum is conserved.
- Total momentum of the system (or Cradle) is conserved.
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- Roosevelt's New Deal faced great opposition from conservative Democrats and Republicans in Congress.
- The counterattack first came from conservative Democrats, led by presidential nominees John W.
- Senator Josiah Bailey (D-NC) released the "Conservative Manifesto" in December 1937, which marked the beginning of the "conservative coalition" between Republicans and southern Democrats.
- The America First Committee launched a petition aimed at enforcing the 1939 Neutrality Act and forcing President Franklin D.
- In that speech he identified the forces pulling America into the war as the British, the Roosevelt administration, and the Jews.