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Work = force × displacement × cos θ. Perpendicular force does zero work.
Net work equals change in kinetic energy.
Without dissipative forces, KE + PE stays constant.
Power = rate of doing work = F · v.
Heat needed to raise 1 kg of a substance by 1 K: Q = mcΔT.
Three modes: conduction in solids, convection in fluids, radiation through vacuum.
Momentum always conserved; KE only in elastic collisions.