1. Happy π Day!!! I wish I could celebrate with you, but I don’t think you want the stomach bug

2. Pressure Problems Here’s an outline as to how to work through the problems you started yesterday. Try and finish them today or for homework if they’re not done. Remember to bring an irregularly shaped object to class tomorrow.

3. P279 Practice A #1 F g = 50.0 N F water = 36.0 N F unknown = 41.0 N P object = ? p water = 1.00 x 10 3 kg/m 3 p unknown = ? F g – F B = F apparent  Use this equation to find Bouyant Force

4. P279 Practice A #1 (cont.) F g /F B = ρ o /ρ f Use the equation above to find #1: ρ object and #2: ρ unknown. This means you’ll have to do two separate calculations: – 1) using only object and water information – 2) using only object and unknown liquid information

5. P279 Practice A #1 (cont.) 1) 50/14 = ρ object /1000 ρ object = 3571 = 3.571 x 10 3 kg/m 3 The object is made of barium 2) 50/9 = 3571/ρ unknown ρ unknown = 642.7 = 6.427 x 10 2 kg/m 3

6. Practice A For #2, use the mass density equation to find the maximum volume and mass for something with a mass density of 1.00 x 10 3 (that’s when it’ll start to sink) For #3, use Archimedes principle and the mass density equation to find the mass of the water displaced. For #4, the buoyant force will equal the F g since helium balloons float in air. Use the same equation as #1.

7. Answers to Section Review p279 Check your answers: 1.A solid has a definite shape, while a fluid does not; a liquid has a definite volume, while a gas does not. 2.b, c, and d 3.4.7 x 10 3 m 3 4.9.92 x 10 2 m 3 5.The kayak’s effective density includes the material of and the air within the kayak and is less than water’s density.

8. Practice B p282 It’s important to remember the Pressure Equation and Pascale’s Principle: – Pressure: P = F/A Pressure = Force/Area – Pascal’s Principle Pressure applied to a fluid in any container spreads equally throughout the container. Check out Figure 6 – the pressure on the button is equal to the pressure on the truck lift

9. Practice B p282 #1 In order to solve for #1, remember that the pressure on the lift is equal to the pressure on the button: F button /A button = F lift /A lift r button = 5.00cm (use this to find the area of the button) r lift = 15.0cm F lift = 1.33 x 10 4 N F button = ? P lift = ?

10. Practice B p282 #1 (cont) F button /0.07065 = (1.33 x 10 4 )/0.00785 F button = 1.19 x 10 5 N P lift = (1.33 x 10 4 )/0.00785 = 1.694 x 10 6 Pa

11. Practice B p282 For #2: remember that pressure is exerted evenly throughout the water bed, so if you can find F g and Area, then you can find the pressure. For #3: the area of the eardrum stays the same, but the force and pressure change from the bottom to the top of the mountain.

12. Section Review p283 Check your answers 1.A 2.3.59 x 10 6 Pa 3.5.0 x 10 6 Pa; 5.0 X 10 1 4.20.1 m **Pa is Pascal, which is the unit of measurement for Pressure

13. Don’t Forget! The AP night is tomorrow (Thursday) at 6pm. We’ll be setting up the catapults and anything else you can think of. Try and be there by 5:45pm. Take a book home if you need to finish anything from today.