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2012_1061_Lecture_Ch_078

# 2012_1061_Lecture_Ch_078 - Work and Energy Chapter 7 Work...

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Work and Energy Chapter # 7

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Work and Energy This chapter is related to the important concept of energy and the closely related concept of work. We start with the definition of work of a constant force The work done by the force is given by the scalar product of the force by the displacement It is the product of the displacement magnitude by component of the force parallel to the displacement
Work applied on an object by a person lifting an object and walking horizontally. In the example on the left side picture each acting force is perpendicular to the displacement, therefore the work of each force is zero. When the force is perpendicular to the displacement the work of that force is zero In conclusion following the physics definition of work in the given example there

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Work performed to pull the crate A person pulls a 50-kg crate 40 m along a horizontal floor by a constant force F p = 100 N, which acts at a 37º angle as shown in the figure. The floor is smooth and exerts no friction force. Determine (a) the work done by each force acting on the crate, (b) the net work done on the crate a) b)
Example Determine the work a hiker must do on a 15.0 kg backpack to carry it up the hill of height 100 m. Determine the work done by gravity on the backpack, and the net work done on the backpack. Assume the motion is smooth and at constant velocity (i.e. acceleration is zero).

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Applying Newton’s second law
Work done by a specific force; example work done by the hiker on the backpack but thus Note that the work depends only on the elevation h , not on the angle. The hiker would do the same work if he lifts the backpack a height h .

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Does the Earth work on the Moon?

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