Work through the two formulas the HESI A2 physics subtest uses for mechanical energy, kinetic energy KE = 1/2 × m × v² and gravitational potential energy PE = m × g × h, and see why the total stays conserved as one form converts into the other.
ObjectiveP.3.1Read4 minExam weightEnergy and Momentum ≈ 20% of Physics
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Calculate the kinetic energy of a moving object from its mass and velocity
Calculate the gravitational potential energy of an object from its mass, height, and the local strength of gravity
Explain why total mechanical energy stays constant while energy converts between kinetic and potential forms
What the lesson concludes
Kinetic energy is KE = 1/2 × m × v² and gravitational potential energy is PE = m × g × h, both measured in joules.
Velocity is squared in the kinetic energy formula, so doubling an object's speed quadruples its kinetic energy, not doubles it.
Potential energy is always measured against a reference height you choose, so fix that reference before you calculate h.
In an idealised system with no friction or air resistance, total mechanical energy, kinetic plus potential, stays constant as energy converts between the two forms.
The joule is the shared unit for kinetic energy, potential energy, and work, which is why a single HESI question can mix all three.