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Unformatted text preview: [4pt] You push a block of mass across a table at speed while applying a constant power
. After you stop pushing, the block slides a distance before coming to rest. Which of the
following is a correct expression for the power ? Sorry, the correct answer was omitted from the choices, but that means everyone gets
credit. If you have to push with power to keep the block moving, then friction is
applying power – to the box. When you stop pushing, only the frictional power is still
applied to the box, so , using the work-energy theorem and the definition of power. Since the box decelerates at a constant rate,
w he r e is the velocity while it was being pushed. Thus, and (b) [4pt] The potential energy of an object as a function of position is
where is measured in Joules and is measured in meters. Where would the object be located
if it was in stable equilibrium?
m m The equilibrium position is where Setting gives m m with so the answer is C. Note: the equilibrium position is not where
. The definition of potential
energy is always arbitrary up to an additive constant, so no physical meaning can be
attributed to one particular value. Only difference...
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