Work Notes Work - when a force (F) causes an object to move a distance (d) in the same direction as the force. Work = Force x distance W=F∙d

Direction of the motion Facts About Work: An object must move for work to occur. 2. That motion must be in the same direction as the force that was applied. Direction of the force Direction of the motion

How is work Measured? (unit) Work formula: W=F·d Force (F) is measured in Newtons (N) Newtons are measured with a spring scale Distance (d) is measured in meters (m) We must convert all distances to meters Work (W) is measured in Newton meters (Nm) ↓ Work = Force x distance W=Fd W=Nm

Simple machines do not change the amount of work done Simple machines just make work “easier” They do this by increasing the distance of the work, which decreases the force needed to do the work. W =↓F x d↑ 1. Work stays the same 2. Distance Increases ↑ 3. Force Decreases ↓

A boy gets angry and punches a wall with a force of 20N A boy gets angry and punches a wall with a force of 20N. The wall does not move. His mother carries a stuffed animal to him using a 3N force and walking a distance of 5 meters. Who did more work? Boy W=F∙d W=20N∙0m W=0Nm Mom W=F∙d W=3N∙5m W=15Nm

A girl wants to throw away a rotten apple A girl wants to throw away a rotten apple. To do this she must (A) pick up the apple, (B) horizontally move it across the table and (C) lower the apple into the trash. Identify for A, B, C situations when she is doing work. Explain your answer. A girl wants to throw away a rotten apple. To do this she must (A) pick up the apple, (B) horizontally move it across the table and (C) lower the apple into the trash. Identify for A, B, C situations when she is doing work. Explain your answer. A.) She has done work. The object is moving in the direct of her force. B.) She has done work. C.) She has not done work. Gravity did the work for her. The object is not moving in the direct of her force, but the direction of gravity's force.

B.) How much work does Rad do? Rad pushes a block 6 meters up an incline plane (ramp) using a force of 10N. Rad’s dad lifts straight up the same block to a height of 1 meter using a force of 60N. 1 m e t r A.) How much work does Rad’s dad Father do? W=F∙d W=60N∙1m W=60Nm B.) How much work does Rad do? W=F∙d W=10N∙6m W=60Nm

Suppose you want to get to the top of a hill Suppose you want to get to the top of a hill. Which path will require the least amount of work to get to the top? Path B Climbing up the steep hill Path A Walking up the long hill

Both paths require the same amount of work to get to the top. If you chose path A… then you are wrong! If you chose path B… then you are also wrong! Both paths require the same amount of work to get to the top.

Warm-up (8/30/16) Is this woman doing work on the box according to the force and motion arrows? In the first situation? Yes or no? Why or why not? In the second situations? Yes or no? First Situation ↑ Work is done on the bin because force and motion are in the same direction. Second Situation ↑ No work is done on the bin because force and motion are in different directions.

Warm-Up (9/1/16) You lift a box with 10 Newtons of force onto a moving truck that is 1.5 meters high. How much work did you do? It takes 5 Newtons of force to push the same box onto a moving truck using a ramp that is 3 meters long. How much work did you do? (Assuming no friction on the ramp)

As you saw from the previous examples: If you move the SAME object to the SAME location, it is the SAME WORK!

For work to occur on an object: Object must move a distance Direction of the movement must be in the same direction as the force Force (→) Movement (→) Work = Force x distance (W=Fxd) Force is measured in Newtons Distance is measured in meters Work = Newtons x meters (W=Nm) Work is measured in Newton meters Simple machines do not change the amount of work, they just make work feel easier by increasing the distance of the work, which decreases the force needed to do the work. W =↓F x d↑ Works stays same Force decreases Distance increases Friction - the force resisting motion on solid surfaces Friction causes objects in motion to not continue moving in the same direction forever and ever. 6. If you move the SAME object to the SAME location, it is the SAME WORK! 7. Water is the least dangerous chemical to mix with