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Module 5: Advanced Mechanics

Quick questions on Gravitational potential energy and escape velocity explained: HSC Physics Module 5

5short 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 escape velocity?
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Escape velocity vescv_{\text{esc}} is the minimum speed needed at a distance rr for an object to reach infinity with zero remaining kinetic energy. By conservation of energy:
What is wrong reference point?
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Zero potential energy is at infinity, not at the planet's surface or centre.
What is q1?
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Write the formula for gravitational potential energy of a mass mm at distance rr from a body of mass MM and explain the choice of zero. [2 marks]
What is q2?
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A 250 kg250 \text{ kg} payload is moved from the surface of Earth to a circular orbit at altitude 500 km500 \text{ km}. Calculate the change in gravitational PE. [4 marks]
What is q3?
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A 1500 kg1500 \text{ kg} spacecraft is fired straight up at 9.0 km/s9.0 \text{ km/s} from Earth's surface. (a) Calculate its total mechanical energy. (b) Find the maximum height above Earth's centre reached.

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