the field lines at the position of the loop. No change in magnetic flux means
no induced emf and no induced current.
- E If the efficiency of the engine is 25%, then the energy that is output for
useful work is 25% of the input energy, which is (25%)(800 J) = 200 J. The
remaining 800 J − 200 J = 600 J is expelled as waste heat.
- C Label the charges 1, 2, and 3, in order from left to right. We’re asked
to find the force on Charge 1 due to the other two charges. The electrostatic
force on Charge 1 due to Charge 2 is a repulsive force, of magnitude ,
and the electrostatic force on Charge 1 due to Charge 3 is a weaker, attractive
force, of magnitude. Since these individual forces act in
opposite directions, the magnitude of the net force is found by subtracting the
magnitudes of the individual forces. So, the total electric force on Charge 1
has magnitude
- A In order for total internal reflection to occur, the beam must be incident in
the medium with the higher index of refraction and strike the interface at an
angle of incidence greater than the critical angle. Since v 1 < v 2 , the refractive
index of Medium 1, must be greater than the index of Medium 2 (n 2 = c/v 2 ),
and the critical angle is θcrit = sin−1 (n 2 /n 1 ) = sin−1 (v 1 /v 2 ).
- E The frequency of the oscillations, f, can be found from the equation f =
. Since k is known, all we need is f in order to calculate m. If we
know the quantity given in E, we can double it to get the period, then take its
reciprocal to obtain f.
- B When the block is at Point Y, all its energy is due to the potential
energy of the stretched spring, which is kd^2. At the moment the block passes
