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Welcome. Per-Eric Åhlén and Morgan Leander Karlstads University, Sweden. Karlstad. Resonance with musical box. Oscillation together with the wall?. Modern Physics. Photoelectric cell. r. r. i. i. REFLECTION. Polarisation. Unpolarized light. Polarized light.
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Welcome Per-Eric Åhlén and Morgan Leander Karlstads University, Sweden Karlstad
Resonance with musical box Oscillation together with the wall?
Modern Physics • Photoelectric cell
r r i i REFLECTION
Polarisation Unpolarized light Polarized light
To the right we imagine an light wave incident from the left onto a polaroid filter. If the incident wave is unpolarised, then one-half of the wave will emerge from the polaroid filter. • We call this orientation of the polaroid zero degrees, and the orientation is indicated by a red arrow. • If we place a second filter behind the first with the same orientation, the second filter has no effect: one-half of the incident beam emerges from the first filter and all of that beam emerges from the second filter. • If we place a second filter behind the first one that is oriented at 90 degrees relative to the first one, no light emerges from the second filter. This is perhaps expected, since the 2 polarisations that are being selected by the filters are perpendicular to each other. This is also the result predicted by Malus' Law.
It was a stack of coin What does Newton laws say?
Rotating eggs Which one is raw and which one is boiled?
Snatch or not • Which thread breaks first if you pull slowly respectively fast? • Give a physical explanation
In which direction will it roll? • If the spool is pulled horizontally to the right, • in which direction will it roll? • to the left? • to the right? • others ... • Think about it！！！ And explain why ? • What if it is pulled in the following way?
F a F a Torque = Force magnitude • lever armτ = F • a
1/2 1/4 Is this realy possible? • Do you see the pattern?
m M How much can you lift? • M = m•eΘf (m=0,1 kg, f = 0,3) Θ= 11π (5,5 turn): M=3200kg Θ: 31,5 turn: M= 6•1024 kg (the earth) Θ: 52 laps: M = 4 •1041 kg (the Milky Way)
Golfplayer • F = ma • F = m· v/ t • F·t = m · v At start vo=0 F·(t -0) = m · (v-0) F·t = m · v
K Particeltheory about air • Materiel: A syringe. • Intention:Three event in daily life • A suction cap sits on the tiled wall in the bathroom. Why is it so hard to loose. • A football is pumped up. It gets harder and harder but not bigger. Why? • Freshly boiled jam is poured when it is hot into a pot. The pot is put into the refrigerator. Then it gets cold it is almost impossible to open. Why? What is common with this three course of events?
There are billions of billions molecules bouncing on the plunger, pushing it out. Still it isn’t moving. There are also a lot of molecules bouncing on the outside of the plunger, pushing it in. K K Why isn’t the plunger moving?
Hold the thumb for the spout and push. There is a lot of space between the molecules. It is vacuum. Therefore you push the molecules closer to each other. K K Starting position of the plunger. Starting position of the plunger. Why can you press air together?
K Why will the resistance increase the more you push? • The molecules come closer together and the bounces against the plunger per second will be more compared with the starting point. But on the outside it will be the same as before. The pressure from the inside of the syringe is greater. Therefore will the plunger return to the starting point if you let it loose.
K K Heat supply The plunger moves out Why will an amount of air expand when it is heated? • The heating makes the molecules mowing faster and bounces more on the inside of the plunger than the outside.
Vacuum • A syringe with the plunger at the bottom. Hold the thumb for the spout and pull. No air can leak in. What will happen? • Explain your prediction with help of the theory about air. If possible repeat the experiment. • Explanation: It is vacuum in the syringe. When you pull the plunger is the molecules pushing on the outside of the plunger and the air pressure is bigger on the outside
1. 2. 3. Vac-uum H2O H2O H2O Another experiment with a syringe 1. Push the plunger to the bottom I a syringe. 2. suck up 1 -2 cm water in the syringe. 3. Hold the thumb for the spout and pull. No air can leak in. What will happen?
1. 2. 5. 3. 4. 1.The battery send out a lot of workers in the wire. The amount of workers per second we usually call current. 2.The workers have negative charge and seek the positive terminals of the battery. The voltage makes them move. 3.The workers slow down, that is to say, meet resistance e.g. in the steel wood. The voltage is the same. That is the work they are doing in the steel wool. 4.The workers spend their energy and get hot e.g. the steel wool. 5.The workers have emitted their energy and the voltage falls. They need new energy let us go to the battery.
Magic Ballon at the wall • How is it possible?
Playing on straw • It´s about standing waves
