A hoop and disc have same mass and radius. Their rotational K.E are related by an equation______________?
Correct answer: B. K.E hoop = 2K.E disc
- A. K.E hoop = K.E disc
- B. K.E hoop = 2K.E disc
- C. K.E hoop = 1/2K.E disc
- D. K.E hoop = 4K.E disc
Explanation
Rotational kinetic energy is 1/2 Iω². For the same mass and radius, a hoop has I = MR² while a disc has I = 1/2 MR², so K.E hoop = 2K.E disc. The common mistake is choosing equality because both objects have the same mass and radius, while ignoring their different mass distributions.
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About Kinetic Energy
Kinetic energy is the energy of motion, given for a nonrelativistic object by K = ½mv², so it depends on mass and the square of speed. Questions connect kinetic energy with work through the work energy theorem, calculate changes in kinetic energy, and distinguish it from momentum and potential energy.
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