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WorkIs done when the Force (F) applied to an object causes that object to be displaced (d) in the same direction as the force applied.
Is a method of transferring energy
How can we ?
The ground is doing work on us.
http://2.bp.blogspot.com/-EsjHgHyE0Xo/VU-Mz9UejGI/AAAAAAAALq4/MOdF14vdUv8/s1600/walk1.jpg
Time for some problem solving!
Suppose a woman is pushing a grocery cart with a 500 Newton force along the 7 meter aisle, how much work is done in pushing the cart from one of the aisle to the other?
http://www.google.com.ph/imgres?imgurl=http://vectortoons.com/wp-content/uploads/2015/02/shopping-collection-sarah-004.jpg&imgrefurl=http://vectortoons.com/product/a-woman-pushing-a-shopping-cart-inside-the-supermarket/&h=904&w=1024&tbnid=lU4J2cTaNdNsnM:&zoom=1&docid=i94W7CJRHFiiOM&ei=4IN1VbmxJ5H3oAT-v4OwCQ&tbm=isch&ved=0CC4QMygqMCo4ZA
Time for some problem solving!
The librarian found a book of mass 1kg is on the floor. If the book is lifted by the librarian from the floor to the top shelf which is 2 meters from the floor, how much work is done on the book?
http://bloximages.chicago2.vip.townnews.com/nwitimes.com/content/tncms/assets/v3/editorial/9/bb/9bbd9852-8a43-5056-8293-3e2c919deff5/506d0316cf7a7.preview-620.jpg
Kinetic Energy (KE)Is the energy of a moving object
Quantifies the amount of work an object can do because of its motion
Work-energy principle
The net work done on an object is equal to the change in the objects kinetic energy.
Concept Check
What will happen to the KE of an object if its mass is doubled but the velocity remains the same?
How about if the velocity is doubled but the mass remains the same?
Time for some problem solving!
A 1000kg jeepney has a velocity of 17 m/s. What is its kinetic energy?A 2000kg jeepney has a velocity of 17 m/s. What is its kinetic energy?A 1000kg jeepney has a velocity of 34 m/s. What is its kinetic energy?
http://www.paulancheta.com/weblog/images/07-04-2-jeepney.jpg
Potential EnergyIs energy gained in raising an object from the
ground or lost when made to fall
Also known as gravitational potential energy
Highest PE PE decreases as KE increases
http://scienceblogs.com/startswithabang/files/2011/12/kinetic_energy_c_la_784.jpeg
Time for some problem solving!
What is the potential energy of a 1 kg book lifted to a 0.5m height above a table?
What is the potential energy of a 1 kg book lifted to a 1.5m height above a table? http://etc.usf.edu/clipart/63200/63282/63282_books_table_lg.gif
Elastic Potential Energy
depends on an elastic material’s elasticity and how much the material is stretched or compressed
http://images.wisegeek.com/spring.jpg
Hooke’s LawWithin an elastic limit, there is direct proportionality between the force needed to stretch or compress elastic materials and their change in elongation
Time for some problem solving!
A 50.0kg marathon runner runs up the stairs to the top of the approximately 350m-tall MSHS building. To lift herself to the top in 15.0minutes, what must be her average power output?