A rocket with a mass of 750 grams is launched straight up. It achieves a velocity of 25.00 m/s in 2.00 seconds. The average net force on the rocket is
A. 16.7 N.
B. 24.5 N.
C. 33.1 N.
D. 41.7 N.
E. 52.8 N.
A. 16.7 N.
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First Law of Thermodynamics: A sealed rigitd tank contains 30 moles of an ideal gas, at an initial temperature of 270 K. The pressure of the gas is increased until the final pressure equals 1.40 times the initial pressure. The heat capacity at constant pressure of the gas is 32.0 J/mol ? K. What is the change in the internal (thermal) energy of the gas during this process? (R = 8.31 J/mol ? K)
A. 77 kJ B. 100 kJ C. 130 kJ D. -50 kJ E. -23 kJ
A thermocouple (0.8-mm-OD wire) used to measure the temperature of quiescent gas in a furnace gives a reading of 165°C. It is known, however, that the rate of radiant heat flow per meter length from the hotter furnace walls to the thermocouple wire is 1.1 W/m and the convective heat transfer coefficient between the wire and the gas is 6.8 W/(m2K). With this information, estimate the true gas temperature. State your assumptions and indicate the equations used.
GIVEN
• Thermocouple (0.8 mm OD wire) in a furnace
• Thermocouple reading (Tp) = 165°C
• Radiant heat transfer to the wire (qr/L) = 1.1 W/m
• Heat transfer coefficient ( ch ) = 6.8 W/(m2 K)
FIND
• Estimate the true gas temperature (TG)
ASSUMPTIONS
• The system is in equilibrium
• Conduction along the thermocouple is negligible
• Conduction between the thermocouple and the furnace wall is negligible
SKETCH
Gamma rays are photons with very high energy. How many visible-light photons with a wavelength of 500 nm would you need to match the energy of a gamma-ray photon with energy 4.1 × 10-13 J? (h = 6.626 × 10-34 J ? s, c = 3.00 × 108 m/s)
A) 1.0 × 106 B) 1.4 × 108 C) 6.2 × 109 D) 3.9 × 103
Two long, parallel wires carry currents of 20.0 A and 10.0 A in opposite directions (Fig. OQ30.9). Which of the following statements is true? More than one statement may be correct