On a cold morning, the rear window defroster on a 2002 Pontiac Aztek supplies 240 Watts of power to clear 0.794 kg of frost (ice), initially at -5.00°C. If all of the energy supplied goes to clearing the ice from the rear window, how long will it take?

A 1.00-L insulated bottle is full of tea at 90.0°C. You pour out one cup of tea and immediately screw the stopper back on the bottle. Make an order-of-magnitude estimate of the change in temperature of the tea remaining in the bottle that results from the admission of air at room temperature. State the quantities you take as data and the values you measure or estimate for them.

Calculate the rate of steady heat transfer from a 8 m-by-10 m roof of a building during a cold winter day. The roof temperature can be assumed to be constant at 12°C. The air temperature outside the building is -5°C. The sky temperature is -17°C. The solar irradiation at the location is 500 W/m². The convection coefficient can be assumed to be 8 W/m².°c. The emissivity of the roof is 0.75, and solar absorptivity is 0.4. Neglect any conduction via the walls to the ground. 2173 W

Seals may cool themselves by using thermal windows, patches on their bodies with much higher than average surface temperature. Suppose a seal has a 0.030 m2 thermal window at a temperature of 30∘C. If the seal's surroundings are a frosty -10 ∘C, what is the net rate of energy loss by radiation? Assume an emissivity equal to that of a human.

A concrete slab is 12.0 cm thick and has an area of 5.00 m2. Electric heating coils are installed under the slab to melt the ice on the surface in the winter months. What minimum power must be supplied to the coils to maintain atemperature difference of 20.0°C between the bottom of the slab and its surface? Assume all the energy transferred is through the slab.

A pronghorn antelope can run at a remarkable 18 m/sm/s for up to 10 minutes, almost triple the speed that an elite human runner can maintain. For a 32 kgkg pronghorn, this requires an astonishing 3.4 kWkW of metabolic power, which leads to a significant increase in body temperature. If the pronghorn had no way to exhaust heat to the environment, by how much would its body temperature increase during this run? (In fact, it will lose some heat, so the rise won't be this dramatic, but it will be quite noticeable, requiring adaptations that keep the pronghorn's brain cooler than its body in such circumstances.) Assume the efficiency of the pronghorn to be equal to that of human.

Seals may cool themselves by using thermal windows, patches on their bodies with much higher than average surface temperature. Suppose a seal has a 0.030 m2 thermal window at a temperature of 30°C. If the seal’s surroundings are a frosty -10°C, what is the net rate of energy loss by radiation? Assume an emissivity equal to that of a human.

For bacteriological testing of water supplies and in medical clinics, samples must routinely be incubated for 24 h at 37°C. A standard constant - temperature bath with electric heating and thermostatic control is not suitable in developing nations without continuously operating electric power lines. Peace Corps volunteer and MIT engineer Amy Smith invented a low - cost, low-maintenance incubator to fill the need. The device consists of a foam-insulated box containing several packets of a waxy material that melts at 37.0°C, interspersed among tubes, dishes, or bottles containing the test samples and growth medium (food for bacteria). Outside the box, the waxy material is first melted by a stove or solar energy collector. Then it is put into the box to keep the test samples warm as it solidifies. The heat of fusion of the phase-change material is 205 kJ/kg. Model the insulation as a panel with surface area 0.490 m2, thickness 9.50 cm, and conductivity 0.012 0 W/m ∙ °C. Assume the…

For bacteriological testing of water supplies and in medical clinics, samples must routinely be incubated for 24 h at 37°C. A standard constant-temperature bath with electric heating and thermostatic control is not suitable in developing nations without continuously operating electric power lines. Peace Corps volunteer and MIT engineer Amy Smith invented a low-cost, lowmaintenance incubator to fill the need. The device consists of a foam-insulated box containing several packets of a waxy material that melts at 37.0°C, interspersed among tubes, dishes, or bottles containing the test samples and growth medium (food for bacteria). Outside the box, the waxy material is first melted by a stove or solar energy collector. Then it is put into the box to keep the test samples warm as it solidifies. The heat of fusion of the phase-change material is 205 kJ/kg. Model the insulation as a panel with surface area 0.490 m2, thickness 9.50 cm, and conductivity 0.012 0 W/m°C. Assume the exterior…

1.2 kg of liquid water initially at 15°C is to be heated to 95°C in a teapot equipped with a 1200-W electric heating element inside. Theteapot is 0.5 kg and has an average specific heat of 0.7 kJ/kg · °C. Taking the specific heat of water to be 4.18 kJ/kg · °C and disregarding any heat loss from the teapot, determine how long it will take for the water to be heated.(Heat loss from the teapot is negligible.)