173
Solving problems (
Смотрите приложение)
1.
A heat engine does 320
J of work, as it takes 700 J
heat from gasoline. What is the internal energy change?
2.
The internal energy of a turbine increases by 280 J
when it does 185 J of work. How much heat did turbine take?
Answer the
questions
in
books from
Literacy on
page (31).
Answer the
174
questions.
Homework
Read the theme 3.4 on page ( 52) and answer the questions on
page ( 19). Solving problems (
Приложение 1.)
Рефлексия
Example
An engine burns 6 kg of fuel and produces 6*10
6
Joules of useful work in 10 minutes.
24*10
6
Joules goes to exhaust.
1.
What is the useful power of engine?
2.
How many Joules does fuel give?
3.
How much energy does 1 kg of fuel give?
Given:
A
useful
= 6*10
6
J
t = 10 min = 600 s
ΔU = 24*10
6
J
Find: P=? , Q = ?, q = ?
Solution and calculation:
1.
A
useful
= P
∙ t 2. Q = A
useful
+
ΔU
6*10
6
J = P∙ 600 Q = 6*10
6
J + 24*10
6
J
P = 10000 W Q = 30 ∙ 10
6
J.
3. Q =
m∙q
30 ∙ 10
6
J = 6 kg ∙ q
Q = 5 ∙ 10
6
J/kg
Problems
3.
A heat engine does 320 J of work, as it takes 700 J heat from gasoline. What is the
internal energy change?
4.
The internal energy of a turbine increases by 280 J when it does 185 J of work. How
much heat did turbine take?
5.
A heat engine does 3000 J of work and releases 2000 J of heat from its exhaust.
What is the efficiency of this engine?
6.
A heat engine with heat efficiency 30% , loses 5000 J heat.
What is the work done by
the engine?
7.
A steam power plant burns 50 tons of coal every hour. The useful power of the plant
is 130 MW. q
coal
= 30 MJ\kg.
a)
How much useful energy does the power plant produce in 1 hour?
b)
How much energy does coal give in 1 hour?
c)
What is the efficiency of this plant?
8.
Power plant of 500 MW of useful has an efficiency of 45%.
a)
What is the useful energy produced by the plant per day?
b)
How much heat energy is released to the surroundings per day?
9.
A heat engine takes 480 J of heat. Work equals to one-fourth (1\4) of change in
internal energy. What is work and internal energy?
10.
An automobile’s motor produces 32 kW of useful power while it travels 40 km at
constant speed of 80 km\h. During the journey it uses 4 kg of diesel fuel. Find the efficiency of the
motor. (q
fuel
= 42 MJ\kg.).
11.
A car travels 300 km at a speed of 75 km\h. Efficiency of car’s engine is 25%.
Useful power is 52 kW. How much diesel fuel did car use? (q
diesel
= 42 MJ\kg.).
12.
Для
работы турбины, развивающей мощность 100000 Вт, за сутки в паровых
котлах сжигается 960 т каменного угля. Определите КПД этой паровой турбины.
13.
Сколько литров бензина расходуется за 1
час двигателем мотоцикла, КПД
которого 11%, производственная мощность 11 л.с ( 1 л.с = 736 Вт)?