# Friction Acquire 2

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Friction Acquire 2

## 1. Initial ideas

### 1.1. Pre-teaching

1.1.1. Forces introduced: air resistance

## 3. ENGAGE

### 3.1. Scenario

3.1.1. Who is the world's fatest man? Not a sprinter but a parachutist! Felix Baumgartner reached a top speed of 833.9mph (1,342km/h) - faster than the speed of sound. He could not have gone any faster than this but why?

### 3.2. Question

3.2.1. why did his speed stop increasing?

### 3.3. Pre-teaching

3.3.1. What air resistance/drag is - resistance from air as object pushes through (there's also surface friction with layer of water - but that might be going too far)

## 4. EXPLORE

### 4.1. Question

4.1.1. How does speed change when an object falls? (will start at zero - will it keep increasing or fall at constant speed)

4.1.2. And can you explain why with forces?

### 4.2. Activity

4.2.1. Do series of tests moving from dropping in air to water to viscous liquid

4.2.2. each time Measure speed quaitatively - as 2 times between equally spaced markers (or elastic bands on measuring cylinder) - if time decreases, it's getting faster, if time same, constant speed

4.2.3. Teacher demonstrates falling object in air - will find it speeds up.

4.2.3.1. Give options for measuring speed

4.2.3.2. 1. Video analysis

4.2.3.3. 2. Motion sensor - presumably some teachers have them!

4.2.3.3.1. Here's a cool one

4.2.3.4. 3. Secondary data

4.2.3.4.1. actual data

4.2.3.4.2. More graphical data here

4.2.3.5. 4. Multiflash camera

4.2.3.5.1. Practical physics details

4.2.4. Two possible objects - most people seem to use stacked coffee filters. Alternatively use a balloon loaded with some wire tied around the mouth. Drop from2-2.5 m standing on a chair- Measure the time for the first 1m, and for the 2nd metre, and see if it decreases.

4.2.5. Test heavy object in water - will speed up

4.2.6. Test lighter object in water - will fall at constant speed

4.2.7. Test heavy object in visous liquid - will fall at constant speed

### 4.3. Discovery

4.3.1. Objects speed up but as increase air resisstance of fluid (from air to water to viscous) objects reach max speed.

## 5. EXPLAIN

### 5.1. Framework

5.1.1. In all fluids will increase initially, but if viscous, air resistance means quickly reaches constant speed (why you measured same speed)

5.1.2. Top speed when forces balanced, no change in speed.

5.1.3. Forces analysis - at beginning weight more than air resistance so speeds up (remmeber there is also upthrust from liquid pushing up)

5.1.4. When faster, pushing more liquid