Latihan Thermodinamika2

SMAK 1 PENABUR Jakarta Fisika Asyik kelas XI semester 2

Nama :__________________ Kls/No:__________/_______

Joshua Untung W.

TERMODINAMIKA

Setiap detik, kita semua

bergerak -

15 hari menjelang akhir kelas XI

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cita-cita kita. 1

During one cycle, an engine extracts 2.00 x 103 J of energy from a hot reservoir and transfers 1.50 x 103 J to a cold reservoir. (a) Find the thermal efficiency of the engine. (b) How much work does this engine do in one cycle? (c) How much power does the engine generate if it goes through four cycles in 2.50 s?

2

A heat engine contains an ideal monatomic gas confined to a cylinder by a movable piston. The gas starts at A, where T = 3.00 x 102 K. See Fig. (a). BC is an isothermal expansion. (a) Find the number n of moles of gas and the temperature at B. (b) Find ∆U, Q, and W for the isovolumetric process A  B. (c) Repeat for the isothermal process BC. (d) Repeat for the isobaric process C  A. (e) Find the net change in the internal energy for the complete cycle. (f) Find the thermal energy Qh transferred into the system, the thermal energy rejected, Qc, the thermal efficiency, and net work on the environment performed by the engine.

3

4.05 x 10-2 mol of monatomic ideal gas goes through the process shown in Figure (b). The temperature at point A is 3.00 x 102 K and is 6.00x102 K during the isothermal process BC. (a) Find Q, ∆U, and W for the constant volume process A  B. (b) Do the same for the isothermal process BC. (c) Repeat, for the constant pressure process CA. (d) Find Qh, Qc, and the efficiency. (e) Find Weng.

SMAK 1 PENABUR Jakarta Fisika Asyik kelas XI semester 2

Nama :__________________ Kls/No:__________/_______

Joshua Untung W. 4

2.00 L of leftover soup at a temperature of 323 K is placed in a refrigerator. Assume the specific heat of the soup is the same as that of water and the density is 1.25 x 103 kg/m3. The refrigerator cools the soup to 283 K. a. If the COP of the refrigerator is 5.00, find the energy needed, in the form of work, to cool the soup. b. If the compressor has a power rating of 0.250 hp, for what minimum length of time must it operate to cool the soup to 283 K? (The minimum time assumes the soup cools at the same rate that the heat pump ejects thermal energy from the refrigerator.)

5

a. How much work must a heat pump with a COP of 2.50 do in order to extract 1.00 MJ of thermal energy from the outdoors (the cold reservoir)? b. If the unit operates at 0.500 hp, how long will the process take? (Be sure to use the correct COP!)

6

A steam engine has a boiler that operates at 5.00 x 102 K. The energy from the boiler changes water to steam, which drives the piston. The temperature of the exhaust is that of the outside air, 3.00 x 102 K. a. What is the engine’s efficiency if it’s an ideal engine? b. If the 3.50 x103 J of energy is supplied from the boiler, find the work done by the engine on its environment.

7

The highest theoretical efficiency of a gasoline engine based on the Carnot cycle is 0.300, or 30.0%. a. If this engine expels its gases into the atmosphere, which has a temperature of 3.00 x 102 K, what is the temperature in the cylinder immediately after combustion? b. If the heat engine absorbs 837 J of energy from the hot reservoir during each cycle, how much work can it perform in each cycle?

8

A steam engine has a boiler that operates at 300OF, and the temperature of the exhaust is 150OF. Find the maximum efficiency of this engine.

9

The energy absorbed by an engine is three times greater than the work it performs. (a) What is its thermal efficiency? (b) What fraction of the energy absorbed is expelled to the cold reservoir?

1 0

A particular engine has a power output of 5.00 kW and an efficiency of 25.0%. If the engine expels 8 000 J of energy in each cycle, find (a) the energy absorbed in each cycle and (b) the time required to complete each cycle. One of the most efficient engines ever built is a coal-fired steam turbine engine in the Ohio River valley, driving an electric generator as it operates between 1 870OC and 430OC. (a) what is its maximum theoretical efficiency? (b) Its actual efficiency is 42.0%. How much mechanical power does the engine deliver if it absorbs 1.40 x 105 J of energy each second from the hot reservoir?

SMAK 1 PENABUR Jakarta Fisika Asyik kelas XI semester 2

Nama :__________________ Kls/No:__________/_______

Joshua Untung W.

11

A gun is a heat engine. In particular, it is an internal combustion piston engine that does not operate in a cycle, but comes apart during its adiabatic expansion process. A certain gun consists of 1.80 kg of iron. It fires one 2.40-g bullet at 320 m/s with an energy efficiency of 1.10%. Assume that the body of the gun absorbs all of the energy exhaust and increases uniformly in temperature for a short time before it loses any energy by heat into the environment. Find its temperature increase.

1 2

An engine absorbs 1 700 J from a hot reservoir and expels 1 200 J to a cold reservoir in each cycle. (a) What is the engine’s efficiency? (b) How much work is done in each cycle? (c) What is the power output of the engine if each cycle lasts for 0.300 s?

1 3

In one cycle, a heat engine absorbs 500 J from a high temperature reservoir and expels 300 J to a low-temperature reservoir. If the efficiency of this engine is 60% of the efficiency of a Carnot engine, what is the ratio of the low temperature to the high temperature in the Carnot engine? A heat engine operates in a Carnot cycle between 80.0OC and 350OC. It absorbs 21 000 J of energy per cycle from the hot reservoir. The duration of each cycle is 1.00 s. (a) what is the mechanical power output of this engine? (b) How much energy does it expel in each cycle by heat?

1 4

A nuclear power plant has an electrical power output of 1 000 MW and operates with an efficiency of 33%. If excess energy is carried away from the plant by a river with a flow rate of 1.0 x 106 kg/s, what is the rise in temperature of the flowing water?

1 5

A 20.0%-efficient real engine is used to speed up a train from rest to 5.00 m/s. It is known that an ideal (Carnot) engine using the same cold and hot reservoirs would accelerate the same train from rest to a speed of 6.50 m/s using the same amount of fuel. If the engines use air at 300 K as a cold reservoir, find the temperature of the steam serving as the hot reservoir.

EKSTRA:

1 mol gas ideal monoatomik mengalami siklus seperti pada gambar berikut. Hitung efisiensinya (nyatakan dalam R) nama proses

W

∆U

Q

A-B B-C C-A

P

∑W = B

600 K

A 300 K

C 450 K V

∑∆U =

∑Q =