A refrigerator has a COP of 2.5. If it removes 7.7 MJ of heat in 25. minutes,
(a) what is the minimum power motor to operate the refrigerator?
(b) what is its efficiency if it were a reversible engine?
(a) 2.1 kW
(b) 29.% efficiency
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An empty train car of mass 2.0 x 104 kg coasts along at 10 m/s. A 3000-kg boulder is suddenly dropped vertically into the car. Find the speed of the car immediately after the boulder is dropped in
What will be an ideal response?
The position of a particle moving along the x axis is given by x = (21 + 22t ? 6.0t2) m, where t is in s. What is the average velocity during the time interval t = 1.0 s to t = 3.0 s?
a. ?6.0 m/s b. ?4.0 m/s c. ?2.0 m/s d. ?8.0 m/s e. 8.0 m/s
A positively charged particle has a velocity in the negative z direction at point P. The magnetic force on the particle at this point is in the negative y direction. Which one of the following statements about the magnetic field at point P can be determined from this data?
a. Bx is positive. b. Bz is positive. c. By is negative. d. By is positive. e. Bx is negative.
What is a hydrocarbon?
A) It is a molecule composed of carbon and hydrogen only. B) It is a wet carbon atom. C) It is any organic molecule. D) It is a molecule derived from hydrogen synthesis. E) none of the above