Where can i find Past papers for physics?

On physics and maths tutor, what does it mean by Unit 1, Unit 2, is that the AS papers? and 3 and 4 Alevel papers?

Unit 1 and unit 2 are AS papers.
Unit 3 were the practical paper they did for old spec for their practicals,so it is good revision material for Paper 3.
Unit4 and unit 5 are the exams for A2,and
Unit 6 IS THE A2 equivalent of Unit 3 and is good revision material for paper 3.

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