Download Unit B—Energy Flow in Technological Systems

Unit B—Energy Flow in Technological Systems
Unit Assessment
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17
Name: _____________________________________
Section B2.0 Quiz
(20 Marks)
1. For each technology listed in the table below, fill in the answers to the following questions:
a) What is the main type of energy conversion evident?
b) Name the scientist chiefly responsible for its discovery.
c) Identify a specific area in science, technology, or society where the device or technology
could be used.
Technology
Main Energy
Conversion
Discoverer
Where It Could Be Used
an electromagnet
a generator
an electric light
a thermocouple
2. Scientists of the early 1600s could not explain the experiment that used Newton’s cradle.
a) Draw a diagram of the demonstration apparatus in the space below.
b) Briefly describe what happens in the demonstration.
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Unit B—Energy Flow in Technological Systems
c) Explain why the ball on the opposite side rises to the same height. Use the theory believed
in the 1600s and compare it with the theory of today.
3. In the space below, draw a labelled diagram of the apparatus that Joule used to prove a
connection between potential energy and heat. Describe how the experiment works.
4. a) What is the weight of a 45.0-kg object?
b) What are three differences between the mass of an object and the weight of the same
object?
5. A 40.0-kg student climbs up a ladder to the roof of a building. The gravitational potential
energy of the student at this point is 2.00 x 103 J. How high is the student above the ground?
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Unit B—Energy Flow in Technological Systems
6. A force of 50.0 N is used to stretch an elastic so that it has 40.0 J of elastic potential energy.
Through what distance was the elastic stretched?
7. A curling rock with a mass of 20.0 kg slides down a sheet of ice at a speed of
6.00 m/s. What is the kinetic energy of the curling rock?
8. A 200-g Nerf dart is shot from a dart gun with a kinetic energy of 3.60 J. What was the initial
speed of the dart?
9. An elastic band is stretched a distance of 15.0 cm by a force of 10.0 N.
a) How much work was done in stretching the elastic?
b) How much elastic potential energy is stored in the elastic?
c) What assumption did you make in answering question (b)?
d) A 1.00-g object is placed on the elastic, and the elastic is released in a vertical direction.
How much kinetic energy is transferred to the object by the elastic?
e) What was the speed of the object at the point that it leaves the elastic?
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Unit B—Energy Flow in Technological Systems
f)
What assumption did you make in answering question (e)?
g) How high will the object in question (d) rise?
h) What assumption did you make in answering question (g)?
10. A 50.0-kg student climbs a flight of stairs a vertical distance of 3.00 m. What is the
gravitational potential energy stored in the student?
11. What principal type of energy conversion takes place in a solar cell? Why are solar cells ideal
for use as energy sources in space?
12. How are a battery and a hydrogen fuel cell alike?
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Unit B—Energy Flow in Technological Systems
Answers to Section B2.0 Quiz
1.
Technology
Main Energy
Conversion
Discoverer
Where It Could Be
Used
[Answers will vary
but could include
the following]
an electromagnet
electric to magnetic
Oersted
lifting magnets in
industry or sucking
coils in appliances
a generator
magnetic to electric
Faraday
electrical generators
an electric light
electric to light
Edison
light bulbs
a thermocouple
heat to mechanical
Seebeck
thermostats
2. a) The diagram should resemble Fig. B2.6 on page 167 of the student book.
b) In the Newton’s cradle experiment, a ball is lifted to a height and released. It collides with
other balls in a row, and a ball at the other end rises to the same height as the original ball.
c) 1600s—This was explained by saying that a living force, vis viva, was being transmitted
through the balls from the motion of the first ball. This force caused the other ball to rise to
the same height.
Present—The first ball is given potential energy when it is lifted away. As the ball returns
to its starting position, it is converting potential energy to kinetic energy. In the collision,
this energy is transmitted to the balls in the row, and the ball on the other side. The ball on
the other side rises to the same height to give it the same amount of potential energy as the
first ball.
3. Explanation: A hanging block of wood attached to a string has potential energy. When
released, the block falls, turning a shaft with attached blades. As the blades rotate with
mechanical energy, the mechanical energy is transformed into heat, thus heating up the water.
4. a) 441 N
b) Mass is scalar; weight is a vector.
Mass is measured in kilograms; weight is measured in newtons.
Mass is constant; weight varies with the value of “g” (acceleration due to gravity).
Mass is defined as the inertia of an object; weight is defined as the gravitational force
acting on a mass.
5. 5.10 m
6. 0.800 m
7. 360 J
8. 6.00 m/s
9. a) 1.50 J
b) 1.50 J
c) work done = energy gain; no energy is lost to other forms of energy
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Unit B—Energy Flow in Technological Systems
d) Ep = Ek = 1.50 J
e) 54.8 m/s
f) Assumed that all the potential energy is converted to kinetic energy
g) 153 m
h) Assumed that all the kinetic energy was converted to potential energy
10. 1.47  103 J
11. Solar energy is converted into electricity similar to a battery. However, the solar cell does not
operate from a chemical reaction like a battery so it never needs recharging or maintenance.
12. A battery and a hydrogen fuel cell both produce electricity.
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