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I need help with these questions. Please provide detailed, clear explanation. Only reply if you will be answering all questions. Thanks!

Chapters 7 & 8: Work and Energy Conservation 1. Under what conditions is the energy of a system conserved? (a) If there are conservative forces acting on the system (b) If conservative forces do work on the system (c) If there are no nonconservative forces acting on the system (d) If nonconservative forces do no work on the system 2. When a person is lifted upward by an elevator at a constant speed, the energy of the person is conserved (a) True (b) False 3. A 12kg box is pushed along a horizontal surface by a force of 18N, applied at an angle 25° above the horizontal. If the horizontal surface has and unknown coefficient of kinetic friction and the crate is pushed for a distance 10m at a constant velocity, how much work is done, in total, on the box? 4. An object, moving horizontally, feels a force: F = (3x2-2x4) where the numeric coefficients in F have the correct SI units implied. (a) Identify all equilibrium points for the motion of this object (b) Which equilibrium points are stable and which are unstable? (c) If the object undergoes a displacement of Ax-3m, how much work is done by the force? 5. A 2000kg car drives along a horizontal road at an initial speed of 15m/s. While driving a distance of 1.2km, the car's engine does 12,000 J of work on the car. What is the speed of the car after traveling the 1.2km? 6. A skydiver will accelerate as the fall, obvious, but not forever; a skydiver will stop accelerating at a speed known as the terminal velocity for that skydiver. While the terminal velocity depends on things ike the temperature and humidity of the air, the altitude of the skydiver, and the surface area of the skydiver's body, it turns out to be roughly the same for all humans

Explanation / Answer

1) Ans: (c) If there are no nonconservative forces acting on the system.

The energy of a system is conserved as long as only conservative forces are acting on the system.

So if we select option (a), then it says that conservative forces are acting but there may be nonconservative forces present as well.

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