1. 2 Work is defined to be the product of the magnitude of the displacement times the component of the force parallel to the displacement W = F ║ d F.

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3 Work is defined to be the product of the magnitude of the displacement times the component of the force parallel to the displacement W = F ║ d F ║ is the component of the constant force F parallel to the displacement d W = Fd cos θ 3

4 Work is a scalar quantity that is only having magnitude which can be positive or negative Unit used is Joule 1 J = 1 N.m 1 J = 10 7 erg = 10 7 dyne.cm 4

5 From the figure, what do you think about the person in dealing with work done on the bag of the grocaries? Apakah pendapat anda tentang kerja yang yang dilakukan oleh orang yang membawa kantong berisi barang belanjaan seperti gambar di samping? 5 Remember that: W = F ║ d W = Fd cos θ

6 6 Considering that work is a scalar quantity, it can be related to vectors product so called dot product W = F. d HOW ???? Where: F = F x i + F y j + F z k d = d x i + d y j + d z k

7 7 In dealing with work, as with force, it is necessary to specify wheter it is about work done by a specific object or done on a specific object. It is also important to specify wheter the work done is due to one particular force (and which one), or the total (net) work done by the net force on the object Berkaitan dengan kerja, sama seperti gaya, penentuan bahwa kerja itu oleh benda atau pada benda sangatlah penting, karena ini mempengaruhi penandaan dari kerja tersebut Termasuk juga kerja yang dikarenakan oleh gaya tertentu (harus dibuat spesifik), atau gaya total pada sebuah objek, ini juga harus ditentukan secara jelas.

8 8 From figure above, determine work done by each force and net work done on the 50-kg crate. Fp = 100 N Dari ilustrasi diatas, berapakah kerja yang dilakukan masing-masing gaya dan kerja total pada kotak bermassa 50 kg

9 9 F net = ma

10 10 Translation Kinetic Energy Work – Energy Principle: the net work done on an object is equal to the change in the object’s kinetic energy

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14 14 1. Gravitational Potential Energy Work by an external force Work by gravity force Gravitational Potential Energy

15 15 2. Elastic Potential Energy

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17 17 Including friction loss Example of a roller coaster subject to frictional forces

18 18 Average Power Instantaneous Power Efisiensi

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