16. A simple pendulum of length L and mass m is attached to a moving support.

 

 

In order for the pendulum string to make a constant angle θ with the vertical, the support must be moving to the:

20. A soap film of thickness t is surrounded by air. It is illuminated at near normal incidence by monochromatic light which has wavelength λ in the film.

 

A film thickness of ____ will produce maximum brightness of the reflected light.

22. A source at rest emits waves with wavelength λ in a medium with velocity v. If the source moves to the right with velocity v_s, the distance between adjacent crests λ’ directly behind the source is:

 

23. Two sources, in phase and a distance d apart, each emit a wave of wavelength λ. See accompanying figure.

 

 

Which of the choices for the path difference ΔL = L₁ – L₂ will always produce constructive interference at point P?

The magnitude of the electric field at point P₁ a distance R₁ from the center is ____. The magnitude of the electric field at point P₂ a distance R₂ from the center is ____.

27. R₄, as shown in the figure, is a variable resistor.

 

In order for there to be no current through the ammeter, R₄ must be equal to:

28. A resistor R dissipates power P when connected directly to a voltage source V, as shown in the accompanying figures.

 

What resistance R' must be connected in series with R to decrease the power dissipated in R to ½P?

29. The infinitely long straight wire carries a conventional current I as shown in the accompanying figure. The rectangular loop carries a conventional current I' in the counterclockwise direction.

 

The net force on the rectangular loop is:

30. A spatially uniform magnetic field of 0.080 T is directed into the plane of the page and perpendicular to it, as shown in the accompanying figure. A wire loop in the plane of the page has constant area 0.010 m². The magnitude of the magnetic field decreases at a constant rate of 3.0 x 10^–4 T/s.

 

What is the magnitude and direction of the induced emf?