Year 7 Science · Unit 3 · Lesson 20

Unit 3 Synthesis — Forces, Energy and Investigation

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Date
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Learning Goals

Warm Up

Compare two

Complete the table to compare a petrol car and an electric car using ideas from the whole of Unit 3.

FeaturePetrol carElectric car
Energy source
Main energy transformation to make it move
Forces acting during braking
Greenhouse gas emissions during use
Energy efficiency (higher or lower, and why)
Biggest environmental advantage or concern

Your Turn

Because… chain

Fill in the missing effects in each box. Each cause leads to the next step in a chain of reasoning that connects forces, energy, efficiency and renewable energy.

Friction between car tyres and the road is a contact force that opposes motion. A car engine applies a driving force forward.
→
The car accelerates (Newton's 2nd Law: net force produces acceleration).
→
The car gains kinetic energy. Some chemical energy is wasted as heat due to friction and engine losses.
→
A petrol engine is only about 25% efficient; an electric motor is about 90% efficient.
→
Australia's electricity grid is transitioning to renewable sources (82% target by 2030).
→

Overall outcome — why switching to electric vehicles powered by renewable electricity matters:

Show What You Know

1. A cyclist rides up a steep hill and then coasts down. Describe the energy transformations during the uphill climb and the downhill coast. Name at least three energy forms and explain where energy is "lost".

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2. Newton's Third Law states that every action has an equal and opposite reaction. Explain how this law applies when a rocket is launched. Identify the action force and the reaction force, and name the objects involved.

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Wrap Up

In one sentence, what was the main idea of this lesson?

HSCScience · Year 7 Science · Unit 3 · Lesson 20 · Apply Worksheet