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Energy stores, KE and GPE
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Energy cannot be created or destroyed. It is only moved between stores. Two equations let you put numbers on it.
Energy stores
Stores include kinetic, gravitational potential, elastic, thermal, chemical, magnetic, electrostatic and nuclear.
Energy is transferred between stores by forces, electric currents, heating and waves.
The total energy is always conserved.
Energy is transferred between stores by forces, electric currents, heating and waves.
The total energy is always conserved.
Kinetic energy
KE = ½ × m × v2
m in kg, v in m/s, KE in joules (J).
Doubling the speed makes the kinetic energy four times bigger.
m in kg, v in m/s, KE in joules (J).
Doubling the speed makes the kinetic energy four times bigger.
Gravitational potential energy
ΔGPE = m × g × Δh
m in kg, g in N/kg, height change in m.
A falling object transfers GPE into KE.
m in kg, g in N/kg, height change in m.
A falling object transfers GPE into KE.
A 2 kg ball moves at 3 m/s. Find its kinetic energy.
- KE = ½ × m × v2
- = ½ × 2 × 32
- = ½ × 2 × 9 = 9 J
Answer: 9 J
Energy is conserved and moves between stores. KE = ½mv2. ΔGPE = mgΔh. Square the speed before multiplying.
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