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VICPhysicsQuick questions
Unit 2: How does physics help us to understand the world?
Quick questions on Work, energy and power: VCE Physics Unit 2 Year 11
10short 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 gravitational PE?Show answer
$PE_g = mgh$ where $h$ is height above a reference point. The reference is arbitrary; only changes in $PE$ matter.
What is elastic PE?Show answer
A spring with spring constant $k$ stretched or compressed by $x$ from equilibrium: $PE_e = \frac{1}{2} k x^2$.
What is falling ball?Show answer
A 0.5 kg ball is dropped from 10 m. Final speed (ignoring air resistance)?
What is spring launch?Show answer
A 0.2 kg ball is launched by a spring with $k = 100$ N/m compressed by 0.1 m. Maximum speed?
What is power of a car?Show answer
A 1500 kg car accelerates from 0 to 27 m/s in 5 s. Average power?
What is forgetting cosine in work formula?Show answer
$W = F d \cos\theta$. If force is perpendicular to motion, no work is done.
What is confusing PE and KE?Show answer
PE is positional (height for gravity, displacement for spring). KE is kinetic ($\frac{1}{2} m v^2$).
What is mixing $W$ as work and $W$ as weight?Show answer
Context matters. Work is energy; weight is a force.
What is power = work/time, not force?Show answer
Power is the rate at which work is done.
What is friction in conservation problems?Show answer
When friction is present, mechanical energy is not conserved; account for the energy loss separately.