H1 Physics 8867 · objective lesson
Energy stores, work and kinetic energy
Track energy transfers across a declared system boundary; work is force times displacement in the force direction and derives the kinetic-energy change.
Repair the common break
Common misconception: Energy is destroyed by an inefficient process.
Correct model: Track energy transfers across a declared system boundary; work is force times displacement in the force direction and derives the kinetic-energy change.
Worked transfer
If friction removes 30 J while a motor supplies 120 J to a cart, its kinetic energy increases by 90 J. Energy is transferred to internal stores; it is not destroyed.
Guided practice
Explain why “Energy is destroyed by an inefficient process.” fails. Then construct one example that correctly applies energy stores, work and kinetic energy.
Independent practice
A 2.0 kg block starts from rest and is pulled 5.0 m by a 14 N horizontal force against 6.0 N friction. Find its final speed.
Return to the recorded repair plan when the explanation and application are secure enough to re-test.