True False Work cannot be done in the absence of motion. True False Work is done

Question

True False Work cannot be done in the absence of motion. True False Work is done when the form of energy changes. True False Without friction or work by an external force, the sum of the potential and kinetic energies of a body is constant. True False Energy conservation law for a projectile (no friction): Potential energy increase equals the kinetic energy decrease. True False More power is required while slowly lifting a box than while lifting it up quickly. True False A source of energy is required to do work.

Explanation / Answer

TRUE Without friction or work by an external force, the sum of the potential and kinetic energies of a body is constant. ... unless you can dream up another energy drain like E=mc^2 TRUE A source of energy is required to do work. TRUE Less power is required while slowly lifting a box than while lifting it up quickly. ... a small motor is required if you lift a big weight slowly. TRUE Work is done when the form of energy changes. ... Generally, the form of energy changes when work is done. If you lift a weight, the energy is consumed in friction (heat) and potential energy. TRUE Energy conservation law for a projectile (no friction): Potential energy decrease equals the kinetic energy increase. A gun power or pendulum starter can transform from potential energy to kinetic energy. FALSE Work can be done in the absence of motion. Work is force over distance.

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