Download Questions on unit 2

Questions on unit 2
Lesson 1
I. Complete the following statements:
1. energy is the ability to do work.
2. sound and heat energies are forms of energy.
3. sun, waterfalls and fuel are from the sources of energy.
4. We obtain light and heat energy from electric lamps and heat
energy from ovens.
5. The food burns inside the body producing chemical energy
6. kinetic energy is used to turn windmills which generate
electricity.
7. In the solar heater, the solar energy is converted in to heat
Energy.
8. sun is a permanent source of energy.
9. chemical energy is Stored in the car battery
10. The electric energy is converted into kinetic energy in fan
11. In the solar batteries, the solar energy changes in to electric
energy.
12. When an object falls from up to down, the kinetic energy
increases while potential energy decreases.
13. In the car engine, the chemical energy changes into heat
energy and then into kinetic energy .
14. When an object is thrown upwards, its velocity decreases ,so
its kinetic energy decrease .
15. An object of mass 2 kg is moving at speed of 4 m/s has a
kinetic energy = 1/2 mv2 = 0.5 x 2x 16= 16 joules.
16. In the filament of electric lamp, the electric energy is
converted into light and heat energies.
17. An object of 20 Newton weight is placed at 5 meter height, it
had a potential energy=100 Joule
18. As doubling height of an object .so the P.E is increased to
double value.
19. Potential energy stored in an object increases as weight and
height increase.
20.The kinetic energy = ½ X m X v2
II. Choose the correct answer:
1. An object of mass 2 kg is moving at a speed of 4 m/s has a
kinetic energy equals …………….. joules.
a.16
b.64
c.32
d.128
2. An object of 20 N weight and it is placed at a height of 5 m,
so its potential energy is ..................... joules.
a.50
b. 150
c. 100
d.200
3. When the velocity of a moving object is doubled, its kinetic
energy ……………………………
a. will not change.
b. will be four times its value'
c. will be doubled
d. will be three times its value.
4. Kinetic energy= .......................
a. ½ mass x (height)2
b. height x (velocity)2
c. ½ mass x (velocity)2
d. weight x (velocity)2
5. Potential energy= ……………………….. .
a. mass x height
b. height + weight.
c. height x weight.
d. weight x velocity
6. When the kinetic energy of an object decreases by 40 J and
its potential energy increases by 40 J, so the mechanical
energy……………….
a. will increase by 80 J
b. will decrease by 40 J.
c. will not change
d. will increase by 40 J'
III. Write the scientific term for each of the
following:
1. The ability to do work.
Energy
2. A form of energy which is produced from speakers'
sound energy
3. The energy which is produced from the battery'
Electric energy
4. A kind of energy stored in the food.
5. Chemical energy
6. The stored energy in an object due to its new position'
Potential energy
7. The work done during the motion of an object'
Kinetic energy
8. The sum of the potential and kinetic energies'
Mechanical energy
9. The product of multiplying the weight of an object by its
height from the ground'
Potential energy
10.
The factor that affects the potential energy of
different objects having the same weight'
Height
11. The factor that affects the potential energy of different
objects at the same height'
Weight
12.
The factor that affects the kinetic energy of
different objects moving with the same velocity.
Mass
13.
T he factor that affects the kinetic energy of
different objects having the same mass
Velocity
IV. What is meant by: look at the school book
1.
2.
3.
4.
5.
6.
7.
Energy
Mechanical energy.
Potential energy.
kinetic energy.
The potential energy of an object=20 joules.
The kinetic energy of an object= 90 joules
The mechanical energy of a moving body= 100 joules.
V. Put () or (x) in front of each of the following
statements and correct the wrong one :
1. Energy is the disability to do work.
X
Ability
2. By raising a ball from the ground, its potential energy
decreases.
X
increase
3. When a stone falls down, its kinetic energy increases. /
4. A bar of chocolate has no energy. X
has energy
5. By kicking the ball, its kinetic energy will increase .
/
6. Work done = Potential energy x Kinetic energy.
X
+
7. Chemical energy is stored in food.
/
8. Potential energy is the stored energy due to the object
motion. X
kinetic
9. Kinetic energy is the work done when the object is at rest.
Potential
10.
Potential energy is affected by the velocity and the
height of the object
weight
11.
Kinetic energy is affected by either weight or velocity
of the object.
Mass
12.
Potential energy of an object will be doubled by
doubling its height.
/
13.
Kinetic energy is inversely proportional to the square
of the velocity. Directily
14.
Potential energy = height + weight.
X
15.
Kinetic energy = mass x (velocity)2
1/2 mass
16.
To increase the kinetic energy of an object four times,
you have to decrease its velocity two times.
/
17.
The potential energy of two identical objects at 5 m
high, have different values.
Same
18.
The kinetic energy of a small car is greater than that
of a bus, because the car mass is less than the mass of the
bus.
Smaller
VI. Give reasons for :
1. Energy is very important to us.
Bec. It is ability to do work
2. Water falls have mechanical energy.
Bec . at the top the water falls has P.E and the motion
of it has K.E
3. some countries try to use the wind energy and solar energy
as sources
Bec. They are cheap and don’t pollute the environment
4. The fuel inside the car is similar to the food inside the body
of the organism.
Bec. Both of them produce the energy which the car
needs to move and which the body needs to do work
5. Potential energy will be doubled by doubling the height.
Bec . the realation between them is direct and P.E=WXH
6. No changes in the potential energy when the object moves
horizontally.
Bec. There is no change in height which is directly
proportional to the P.E
P.E=WXH
7. when a stone is thrown upwards, its potential energy
increase
Bec. The height increase and the relation between them
is direct P.E=WXH
8. when an object is thrown upwards, its kinetic energy
decreases
Bec, the speed decreases and the relation between them
is direct K.E= 1/2 MV2
9. The work done to stop a moving car increases by increasing
the velocity of the car.
Bec . the K.E increases and the relation btween speed
and K.E is direct
K.E= 1/2 MV2