Water flows through a Venturi tube as shown in the diagram. The radius of the large cross section of the pipe is 2 cm and the radius of the constricted portion of the pipe is 1 cm. If the speed of the water in the large cross section pipe is 1 m/s, the pressure difference (P1 - P2) is most nearly
(A) 0.6*102 N/m2 (B) 3*102 N/m2 (C) 1.5*103 N/m2 (D) 7.5*103 N/m2 (E) 37.5*103 N/m2
The Maxwell distribution of molecular speeds in a gas is given by
n(v) = A v2 exp(-mv2/(2kT)),
where A is a constant.
The most probable speed is
(B) (3kT/m)½ (C) (8kT/m)½
(D) 3kT/2 (E) (2π m kT)½
A mole of ideal gas initially at temperature T0 and volume V0 undergoes a reversible isothermal expansion to a volume V1. If the ratio of the specific heats is cP/cV = γ an if R is the gas constant, the work done is
(A) 0 (B) RT0 (V1/V0)γ (C) RT0 (V1/V0 - 1) (D) CVT0 [1 - (V0/V1)γ] (E) RT0 ln(V1/V0)
Electric power is used to heat and melt 3 kg of a certain material. The graph of temperature versus time for the process is shown. A current of 10 A at a potential difference of 100 V is used and the time between t1 and t2 is approximately 15 minutes. The heat of fusion of the material is most nearly
(A) 80 J/kg (B) 970*102 J/kg (C) 144*103 J/kg (D) 340*103 J/kg (E) 539*1032 J/kg
Assuming that all the planets have the same reflection coefficient for sunlight and the same emission coefficient, which of the following relationships would be expected between the planets average temperatures T in Kelvin and their distance R from the sun?
(A) T ∝ R-2 (B) T ∝ R-1 (C) T ∝ R-½ (D) T ∝ R½ (E) T ∝ R2
In terms of the Boltzmann constant, the classical constant-volume specific heat per atom of He gas is
(A) k/2 (B) k (C) (3/2)k (D) 2k (E) 3k
A gas is take through the cycle A --> B --> C --> A as shown. What is the net work done by the gas?
(A) 2000 J (B) 1000 J (C) 0 J (D) -1000 J (E) -2000 J
A thermodynamic system, initially at absolute temperature T1, contains a mass m of water with specific heat capacity c. Heat is added until the temperature rises to T2. The change in entropy of the water is
(A) 0 (B) T2 - T1 (C) mcT2 (D) mc(T2 - T1) (E) mc ln(T2/T1)
Heat dQ flows from a body of temperature T1 to a body of temperature T2. The total change in the entropy of the two bodies is equal to
(A) dQ(1/T1 + 1/T2) (B) dQ(T1 + T2) (C) dQ(T1 - T2) (D) -dQ(1/T1 - 1/T2) (E) dQ/T2
Refer to the following processes involving systems labeled by numbers 1 - 8.
A bar of iron (1) at 300 K is brought into thermal contact with a body (2) at
400 K, the two being thermally isolate from all other systems.
An ideal gas (3) is compressed reversibly while in contact with a reservoir (4), the two being thermally isolate from all other systems.
A body of water (5) freezes reversibly.
A container of water is stirred and its temperature increases by 1 K.
A chemical reaction takes place in an isolated system (7).
A Carnot engine (8) operates in a cycle.
For which of the systems does the entropy decrease?
(A) 1 (B) 4 (C) 5 (D) 6 (E) 7