Systems in Action: Unit Review

a) information b) social c) mechanical d) natural.

Any two: drive (pedals, chain, gears: move forward), braking (slow and stop), steering (change direction).

It has mechanical parts (the bus), social parts (drivers, routes, rules) and information parts (delay and cancellation notices).

Inputs: gasoline, air, the operator's push and control, tall grass. Intended: cut grass. Unintended: noise, exhaust, thermal energy.

Information about the output that goes back to adjust the system, e.g. a thermostat sensing the room temperature.

Unintended. A fridge's purpose is to keep food cold; the thermal energy released at its back is a side effect.

To kill harmful bacteria by heating it (at least 72 °C for at least 16 seconds), then cooling it quickly.

9 × 40 = 360 L.

It removes water without boiling, so less fuel is needed in the evaporator.

First Nations peoples of the eastern woodlands, including the Anishinaabe and Haudenosaunee, and many communities still do today.

Thermostat: control. Flame sensor: safety. Clean filter: efficiency (and health).

Sorting patients by urgency. It mainly makes the system safer, because the sickest people are treated first.

Checking, cleaning and repairing finds worn or broken parts before they fail.

80 × 5 = 400 J.

Force = 4 × 9.8 = 39.2 N. W = 39.2 × 1.5 = 58.8 J.

720 ÷ 12 = 60 N.

0 J: there is no displacement.

720 ÷ 120 = 6.

1.5 ÷ 0.3 = 5.

a) second class b) third class c) first class.

300 × 2 = 600; 600 ÷ 400 = 1.5 m from the middle.

1 000 ÷ 5 = 200 N.

IMA = 5 ÷ 0.5 = 10. Force = 700 ÷ 10 = 70 N.

It turns 3 times more slowly with about 3 times the turning force.

Output = 600 J. Input = 800 J. Efficiency = 600 ÷ 800 × 100% = 75%.

Thermal energy caused by friction (also sound and vibration).

Any two: lubricants, ball bearings, streamlined shapes, low rolling-resistance tires, regenerative braking, lighter materials.

The model's yearly electrical energy use in kWh, compared with similar models.

120 kWh × $0.12 = $14.40 per year.

They warn owners about safety defects and tell them to repair, return or stop using the product.

280 ÷ 40 = 7 times.

The product moved to the workers, and each worker did one step quickly, so no time was wasted walking.

Benefit: more produced, lower cost, safer work. Cost: jobs lost or changed, expensive machines, repetitive work, more energy use.

Sensor: soil moisture sensor. Controller: the computer running the code. Actuator: the valve or pump that turns the water on and off.

Social: safer (less heavy lifting) but some jobs lost. Economic: higher productivity but expensive robots. Environmental: electricity use and future electronic waste (or less wasted space and energy with efficient routing).

Add an else: if dark, turn light on; else turn light off.

Any two: needs and values, laws, safety concerns, population changes, cost, environmental awareness, culture, events like pandemics.

Beans add nitrogen to the soil, which helps the corn and squash grow.

Example: gardener: fresh, cheaper food and exercise, but it takes time and only grows in summer. Environment: food travels a very short distance, and composting returns nutrients to the soil.

Define the problem → plan → build a prototype → test → improve.

Actual MA = 5 ÷ 2 = 2.5. Efficiency = 1.0 J ÷ 1.2 J × 100% ≈ 83%.

Never put hands, feet or head under the hanging load (or: make sure the support is stable; an adult does any cutting).