Work and Energy Work Done W = Fd Units and Direction Positive and Negative Work When Work = 0

Work Work (W) is the energy transferred to an object when a force acting on the object moves it through a distance W = F x d __________

TeachWithFergy Preview File Please enjoy this preview of your Student Version of the Power Point. Some slides appear blank because they have been removed. Student versions have portions of the text removed which is given in the teacher version and appear as ______ Other slides may have ........... on them, this represents writing that has been removed. Please note that the Entire Unit Package can also be purchased at a steep discount from my Store.

Work Done Work is done when you lift an object _______ Work is done to make a car accelerate

Work Consider a situation where you are pulling a bag on wheels at an angle Θ to the displacement ________

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Units and Direction Work is scalar and has no direction Its units are Nm = J __________ Stop at 3:42

Positive or Negative Work If the force and displacement are in the same direction, work is “+”. If F and d are in opposite directions, work is “-” Work is positive, negative, or zero, depending on the angle between the force and the displacement. d = r Try an example on your own for each

If velocity is constant, isn’t a = 0 and therefore, F = 0 and W = 0? Whenever you talk about the work done, you must be very careful to specify which force does the work. i.e. if the object is moving at a constant v Wfriction= Ff x d _________ Wapp = Fapp x d Wnet = Fnet x d x = +1 m Ffriction Fext = 10 N

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Check Your Understanding 2000.0 N of force is applied to a cable used to tow a car as seen below 20.0 km. How much work is being done? Your answer should be in megajoules (1,000,000 J = 1 MJ).

Check Your Understanding A store clerk moved a 4.4-kg box of soap without acceleration along a shelf by pushing it with a horizontal force of magnitude 8.1 N. If the employee did 5.9 J of work on the box, how far did the box move?

Check Your Understanding A toboggan carrying two children (total mass = 85 kg) reaches its maximum speed at the bottom of a hill, and then glides to a stop in 21 m along a horizontal surface. The coefficient of kinetic friction between the toboggan and the snowy surface is 0.11. Draw an FBD of the toboggan when it is moving on the horizontal surface. Determine the magnitude of kinetic friction acting on the toboggan.

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Check Your Understanding A bag of groceries of mass 8.1 kg is raised vertically without acceleration from the floor to a countertop, over a distance of 92 cm. Determine the force needed to raise the bag without acceleration the work done on the bag of groceries against the force of gravity

Check Your Understanding A student pushes against a large maple tree with a force of magnitude 250 N. How much work does the student do on the tree?

Check Your Understanding A 500-kg meteoroid is travelling through space far from any measurable force of gravity (F approaches 0). If it travels at 10,000 km/h for 100 years, how much work is done on the meteoroid?

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Zero Work Done - Summary When W = 0 ______ _________ ___________