Conservation of Mechanical Energy
When only conservative forces do work, KE + PE remains constant throughout the motion.
What is Conservation of Mechanical Energy?
When only conservative forces do work, KE + PE remains constant throughout the motion.
Key formula / rule: KE + PE = constant when non-conservative work is zero.
Key points
- Apply energy conservation to pendulum and track problems.
- Evaluate energy losses when friction is present.
Common exam trap
Applying conservation on rough surfaces.
Definitions
- Term
Conservation of Mechanical Energy
- Meaning
When only conservative forces do work, KE + PE remains constant throughout the motion.
- Term
Conservation of Mechanical Energy — explanation
- Meaning
This is the fastest route through pendulum, roller-coaster and vertical-circle problems, since intermediate forces need not be known. When friction acts, the shortfall equals the heat generated.
Learning objectives
Apply energy conservation to pendulum and track problems.
Evaluate energy losses when friction is present.
Formulae
- Key point
KE + PE = constant when non-conservative work is zero.
- Key point
With friction: DKE + DPE = Wfriction (negative).
- Key point
Energy methods bypass unknown intermediate forces.
Prerequisites
PHY-U1-WEP-T1-S2-C1
Common mistakes
Applying conservation on rough surfaces.
Measuring heights from inconsistent reference levels.
Keywords
Conservation
Mechanical
Energy
Practice preview
A block of mass 0.5 kg is attached to a spring with a spring constant of 200 N/m. If the spring is compressed by 10 cm and then released, what is the maximum speed of the block? (Assume a frictionless surface)…
medium
What is the primary condition for the conservation of mechanical energy in a system?…
easy
A ball is dropped from a height 'h' above the ground. Neglecting air resistance, which of the following statements is true regarding its mechanical energy?…
easy