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4. Work

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In this mini-lecture, we discuss the concept of work in greater detail, focusing in particular on: (i) the equation for work done on a system when there is an angle between the applied force on an object and the direction the object travels; (ii) an example that illustrates a reduction in work done when the force is applied at an angle; (iii) the work-energy principle, where the net work done is equal to the change in kinetic energy of the system; (iv) an example where we calculate the stopping distance of a train braking: and (v) thermal energy as an internal energy of a system, where we see that solids, liquids, and gases have increasing thermal energy in that order.


In this course, Professor Douglas Halliday (Durham University) explores energy. In the first mini-lecture, we discuss the big picture of energy, looking at types of energy, key principles, and units. In the second mini-lecture, we consider changes in energy by looking at examples of various energy exchanges involving kinetic and potential energy, heat, electrical energy, etc. The third mini-lecture introduces the concept of the conservation of energy and works through four related examples. In the fourth mini-lecture, we discuss the concept of work in greater detail and go through a couple of examples. In the fifth mini-lecture, we introduce the concepts of power and efficiency, working through some examples and looking at how to improve the efficiency of a system.


Douglas Halliday is a Professor of Physics at Durham University and a Director at the Durham Energy Institute. His research involves next-generation thin-film photovoltaic (solar) devices. Professor Halliday is also the Director of the Centres for Doctoral Training in Energy and Global Challenges Research as well as the Chair of the European Universities Association Energy and Environment Platform (EUA-EPUE).

Cite this Lecture

APA style

Halliday, D. (2022, January 14). Energy - Work [Video]. MASSOLIT.

MLA style

Halliday, Douglas. "Energy – Work." MASSOLIT, uploaded by MASSOLIT, 14 Jan 2022,

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