PHYS 1145 Lecture 4: Chapter 9 Equilibrium

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indigozebra465

7 Nov 2016

School

Northeastern University

Department

Physics

Course

PHYS 1145

Professor

Assad Fotovatian

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Document Summary

Work: the product of the magnitude of the displacement times the component of the force parallel to displacement. Work done by variable force: in moving an object between two points is equal to the area under the force vs d curve between those two points. Work energy principle: the net work done on an object is equal to the change in the objects kinetic energy. Potential energy: energy associated with forces depending on the position or con guration of an object relative to surroundings. Conservative forces: forces such as gravity for which the work done does not depend on path taken but only on initial and nal positions, potential energy can be de ned only for this force. Nonconservative forces: forces such as frictions, any work they do depends on path. Work energy principal: the work done by no conservative forces acting on an object is equal to the goal change in kinetic and potential energies.

Related Questions

Which of the following statement are true mechanical energy? Include all that apply.

1.The total amount of mechanical energy of an object is the sum of its potential energy and the kinetic energy.

2. Heat is a form of mechanical energy.

3. The mechanical energy of an object is always conserved.

4. When non-conservative forces do work, energy is transformed from kinetic to potential (or vice versa), but the total mechanical energy is conserved.

5. A bowling ball is mounted from a ceiling by way of a strong cable. It is a drawback and released, allowed to swing as a pendulum. As it swings from its highest position to its lowest position, the total mechanical energy is mostly conserved.

6. When a friction force does work on an object, the total mechanical energy of that object is changed.

7. The total mechanical energy of an object remains constant if the only forces doing work on the object are conservative forces.

8. If an object gains mechanical energy, then one can be certain that a non-conservative force is doing work.

lilacplatypus580

Complete the following statement: A force that acts on an object is said to be conservative

a. if the work it does on the object is independent of the path of the motion.

b. it results in a change in the object's kinetic energy.

c.it obeys Newton's laws of motion.

d, it always acts in the direction of motion of the object.

e.the work it does on the object is equal to the increase in the object's kinetic energy.

pucewhale134

1. Can work be done on a system if there is no motion?

A) Yes, if an outside force is provided B) Yes, since motion is only relative C) No, since a system which is not moving has no energy D) No, because of the way work is defined

2. The quantity 1/2 mv 2 is

A) the power supplied to the object by the force B) the work done on the object by the force C) the kinetic energy of the object. D) the potential energy of the object.

3. If you push twice as hard against a stationary brick wall, the amount of work you do

A) doubles. B) is cut in half C) remains constant but non-zero D) remains constant at zero

4. If the net work done on an object is positive, then the object's kinetic energy

A) increases. B) decreases C) remains the same D) is zero

5 A force of 20 N moves an object in the direction of the force. The work done when the object moves from 2.0 to 4.0 m is o A) 20 J OB) 40 J oC) 60 J D) 80 J

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PHYS 1145 Lecture 4: Chapter 9 Equilibrium

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