U4 Videos FP 5.1.11

Under what conditions is mechanical energy conserved?

• When the work done by friction is zero.

• When the work done by the applied force is zero.

• When both the work done by friction and the work done by the applied force are zero.

• When the work done by friction is equal to the change in mechanical energy.

Which equation correctly relates the work done by friction to the change in mechanical energy, assuming no work is done by an applied force?

• Wf = MEf + MEi

• Wf = MEf - MEi

• Wf = MEi - MEf

• Wf = Ff * d

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Which statement correctly describes the direction of the force of friction?

• It is always perpendicular to the surfaces in contact.

• It always acts in the same direction as the sliding motion.

• It is always independent of the direction of the applied force.

• It is always parallel to the surfaces and opposes sliding motion.

In the work done by friction equation (Wf = Ff * d * cos(θ)), what is the typical angle (θ) between the force of friction and the displacement of the object?

• 0 degrees

• 90 degrees

• 180 degrees

• 270 degrees