An elevator is being lifted at a constant speed by a steel cable attached to an electric motor. Which statement is correct?
The cable does positive work on the elevator, and the elevator does positive work on the cable.
The cable does positive work on the elevator, and the elevator does negative work on the cable.
The cable does negative work on the elevator, and the elevator does positive work on the cable
The cable does negative work on the elevator, and the elevator does negative work on the cable.
A lightweight string is wrapped several times around the rim of a small hoop. If the free end of the string is held in place and the hoop is released from rest, the string unwinds and the hoop descends. How does the tension in the string (T) compare to the weight of the hoop (w)?
T = w
T > w
T < w
not enough information given to decide
A block of ice (density 920kg/m3) and a block of iron (density 7800kg/m3) are both submerged in a fluid. Both blocks have the same volume. Which block experiences the greater buoyant force?
the block of ice
the block of iron
Both experience the same buoyant force.
The answer depends on the density of the fluid.
The air in an organ pipe is replaced by helium (which has a lower molar mass than air) at the same temperature. How does this affect the normal-mode wavelengths of the pipe?
The normal-mode wavelengths are unaffected.
The normal-mode wavelengths increase
The normal-mode wavelengths decrease.
The answer depends on whether the pipe is open or closed.
Two identical strings are each under the same tension. Each string has a sinusoidal wave with the same average power Pav . If the wave on string #2 has twice the amplitude of the wave on string #1, the wavelength of the wave on string #2 must be
4 times the wavelength of the wave on string #1.
twice the wavelength of the wave on string #1.
the same as the wavelength of the wave on string #1.
1/2 of the wavelength of the wave on string #1.
In an isothermal expansion of an ideal gas, the amount of heat that flows into the gas
is greater than the amount of work done by the gas.
equals the amount of work done by the gas.
is less than the amount of work done by the gas, but greater than zero.
is zero.
A solid spherical conductor has a spherical cavity in its interior. The cavity is not centered on the center of the conductor. If a positive charge is placed on the conductor, the electric field in the cavity
points generally toward the outer surface of the conductor.
points generally away from the outer surface of the conductor.
is zero.
not enough information given to decide.
Electrons in an electric circuit pass through a resistor. The wire has the same diameter on each side of the resistor. Compared to the potential energy of an electron before entering the resistor, the resistor, the potential energy of an electron after leaving the resistor is
greater.
less.
the same.
not enough information given to decide.
A steady current flows through an inductor. If the current is doubled while the inductance remains constant, the amount of energy stored in the inductor
increases by a factor of 2.
increases by a factor of 4.
increases by a factor that depends on the geometry of the inductor.
In Young’s experiment, coherent light passing through two slits ( S1 and S2 ) produces a pattern of dark and bright areas on a distant screen. If the wavelength of the light is increased, how does the pattern change?
The bright areas move closer together.
The bright areas move farther apart.
The spacing between bright areas remains the same, but the color changes.
any of the above, depending on circumstances
Explain the terms briefly.
(A) Magnetic torque
(B) The zero law of thermodynamics
(C) Doppler effect
For an ideal gas, draw the four kinds (adiabatic, isochoric, isobaric, and isothermal) of thermodynamics processes in a PV diagram (P is pressure and V is volume).Additionally, you must explain the heat, internal energy, and work in the first law of thermodynamics for the four processes.
An electron in the beam of a TV picture tube is accelerated by a potential difference of 2.0kV. Then it passes through a region of transverse magnetic field, where it moves in a circular are with radius 0.180m. What is the magnitude of the field?
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