Work

Review a few things first

What is work? Ted Talk https://www.youtube.com/watch?v=u6y2RPQw7E0 https://www.youtube.com/watch?v=dB36sW-iYBY 3:22

The formula for Work W = Fd

Examples of Work

Non - Examples of Work

Tricks

Example 1: You discover a box of rocks in middle of your room Example 1: You discover a box of rocks in middle of your room. You apply an effort force of 65N to push them 2 meters so they are against the wall. How much work have you done? W = Fd W = 65N x 2m W = 130 J

Example 2: You now have a box of rocks against the wall of your room Example 2: You now have a box of rocks against the wall of your room. You decide you like them where they originally were and push them back to the middle of the room. Now how much work have you done to push them back?

Example 3: The rocks are now in the middle of the room Example 3: The rocks are now in the middle of the room. You decide to lift them straight up 0.8 m and carry them across 5 meters across the room. Now how much work have you done (lifting and carrying)? The rocks have a mass of 25 kg.

Example 4: Who has done more work? Stephanie pushes a 20 kg box with a net force of 60N. She moves it 30 m across the floor in 5 seconds. Dustyn pushes a 20 kg box with a net force of 72N. He moves it 25 m across the floor in 4 seconds. 1800 J 360 W 1800 J 450 W