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## Viscosity!

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**We also need to understand molecules. Molecules are like**particles that are stuck together.**That is important because bigger molecules means higher**viscosity.**If flow rate is slow, viscosity is _____.**high So the molecules are _______. bigger If the flow rate is fast, viscosity is____. low So the molecules are _______. smaller**Variables! The Constant Variable: WE DON’T CHANGE! WE**MUST NOT CHANGE!The Independent Variable: WE CHANGE! WE MUST CHANGE!The Dependent Variable: THIS IS OUR ANSWER!**Balanced Forces: Force that is equal and opposite. (The**same and coming from both sides). Unbalanced Forces: Force that is unequal and opposite. (A strong force on one side, a weak force on the other.) No the particles did not move closer together, just the air came out.**Mr. Wu’s mass is 50 on the moon.**kg Mr. Wu’s weight is 49 on the Moon. newtons P = F/A So, the force is 12,00 newtons And the area is 42.5 so the pressure is… 28.2 pascals**1. Gravity2. Friction3. Tension**The force is balanced if the boy cannot lift the bag. If he can lift the bag, it is unbalanced.**Is the paper clip denser than the water?**Yes, it is!**Why did the paper clip float on the water?**Surface Tension! There is cohesion between the water particles that holds it together.**Let’s play a game! Adhesion or cohesion!?**Cohesion - the bubble’s particles stick to each other.**Adhesion or cohesion!?**Adhesion – the water particles stick to the glass particles**This glue bubble?**Cohesion – the glue particles stick to each other**Glue the paper to the wall?**Adhesion - the glue sticks to the wall**Why did the can implode?**What happens to particles when they lose energy (cool down)? What about the air particles? Are they moving faster or slower?**Balanced Forces: Force that is equal and opposite. (The**same and coming from both sides). Unbalanced Forces: Force that is unequal and opposite. (A strong force on one side, a weak force on the other.) No the particles did not move closer together, just the air came out.**Mr. Wu’s mass is 50 on the moon.**kg Mr. Wu’s weight is 49 on the Moon. newtons P = F/A So, the force is 12,00 newtons And the area is 42.5 so the pressure is… 28.2 pascals**1. Matter**• Solid, liquid, gas, viscosity, • Cohesion, adhesion, 2. Forces • friction, elastic force, static electricity • tension, magnetic force, gravity, balanced • and unbalanced, compression, deformation, • pressure**Forces and Solids**Meh.**But liquids and gases…**We can make them work for us…**Fluids Under Pressure (压力)**Under pressure!**So, what about the forces?**Balanced? Unbalanced!**The air pressure inside your head is the same but outside it**is much less. Probably, just your ears will “pop”**What if there is no pressure?**Vacuum - 真空 – an area with very low pressure. A perfect vacuum has no pressure.**How does it work**The room pressure is the same so it is higher, the air goes in the machine. The machine pushes out the air making a low pressure area.**Remember me?**帅哥？ Pascals are small so we need KILOPASCALS!