Engineering Board Exam Reviewer · Applications: Cooling, Heating, and Mixture Problems · medium

A thermometer reading 10° C is brought into a room at 30° C. It reads 20° C after 3 minutes. What does it read after 6 minutes?

  1. 30° C
  2. 22.5° C
  3. 25° C
  4. 27.5° C

Answer

C. 25° C

Solution

T-30=-20ekt. At t=3: -10=-20e3k e3k= 12. At t=6: T-30=-20· 14=-5 T=25° C.

More Applications: Cooling, Heating, and Mixture Problems questions

  1. Coffee at 90° C is left in a 20° C room and cools to 80° C in 2 minutes. How many minutes after it was poured will it reach 50° C?
  2. Newton's law of cooling states that the rate of change of an object's temperature T is proportional to the difference between T and the…
  3. A body at 100° C is placed in a room kept at 20° C. It cools to 60° C in 10 minutes. What is its temperature after 20 minutes?
  4. A body at 100°C is placed in a room held at 25°C. Using Newton's Law of Cooling dT/dt=k(T-25), if the temperature is 80°C after 10…
  5. For the cooling scenario above (T0=100°C, Ts=25°C, k -0.031 per min), find the temperature after 20 minutes.
  6. A tank initially contains 100 liters of brine with 5 kg of dissolved salt. Brine containing 0.2 kg/liter enters at 3 liters/min, and the…
  7. For the tank problem above (dQ/dt=0.6-0.03Q), find the steady-state (equilibrium) amount of salt as t ∞.
  8. A 50-liter tank contains pure water. Brine with 2 kg/liter of salt flows in at 4 liters/min, and the mixture flows out at the same rate…
  9. Solve the tank equation dQ/dt=8-0.08Q with Q(0)=0.
  10. Water flows into a tank according to dV/dt=k(50-V) with V(0)=0 and k=0.1. Find the volume after 10 minutes.

All Applications: Cooling, Heating, and Mixture Problems questions