Engineering Board Exam Reviewer · Thermodynamics · medium
A closed system rejects 50 kJ of heat while 80 kJ of work is done ON the system. What is the change in internal energy?
- 130 kJ
- −130 kJ
- −30 kJ
- 30 kJ
Answer
D. 30 kJ
Solution
Q = -50 kJ, W = -80 kJ. U = Q - W = -50 - (-80) = 30 kJ.
More Thermodynamics questions
- A 1000-kg car moves at 25 m/s. What is its kinetic energy?
- A body of mass 10 kg is raised vertically by 50 m. What is the increase in its potential energy? (g = 9.81 m/s2)
- An electric water heater rated at 3 kW heats 50 liters of water from 15 °C to 60 °C. Assuming no heat losses, how long will it take? ( = 1…
- How much heat is required to change 1 kg of water at 20 °C into saturated steam at 100 °C and atmospheric pressure? (c = 4.187 kJ/kg· K, h…
- A 0.5-kg copper block (c = 0.385 kJ/kg· K) at 200 °C is dropped into 2 kg of water (c = 4.187 kJ/kg· K) at 25 °C in an insulated…
- How much heat is required to convert 2 kg of ice at −10 °C into water at 20 °C? (cice = 2.09 kJ/kg· K, h if = 335 kJ/kg, cwater = 4.187…
- How much heat is required to melt 2 kg of ice at 0 °C into water at 0 °C? (latent heat of fusion = 335 kJ/kg)
- How much heat is needed to raise the temperature of 5 kg of water from 20 °C to 80 ° C? (c = 4.187 kJ/kg· K)
- How many psi is equal to 1 standard atmosphere?
- An automobile tire has a gauge pressure of 200 kPa at 25 °C. After driving, the temperature of the air rises to 50 °C. Assuming constant…