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Unit 2: How does physics help us to understand the world?

Quick questions on Collisions and conservation of momentum (VCE Physics Unit 2)

4short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is treating KE as always conserved?
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KE is conserved only in elastic collisions.
What is dropping signs in head-on collisions?
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Bodies approaching each other have opposite signs of velocity.
What is applying conservation to a non-isolated system?
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External forces (large friction, gravity over long times) can invalidate the assumption. For typical short-duration collisions on smooth surfaces, the system is effectively isolated.
What is confusing impulse with force?
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Impulse has units of N s (or kg m s$^{-1}$). Force has units of N.

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