Fields In Physics Flashcards
1
Q
What are the two general classes of waves?
A
Mechanical waves and electromagnetic waves.
2
Q
What are mechanical waves?
A
Waves that require a material medium for their propagation.
3
Q
Give examples of mechanical waves.
A
Water waves
4
Q
What are electromagnetic waves?
A
Waves that do not require a material medium for their propagation.
5
Q
What gives rise to electromagnetic waves?
A
The vibrations of electric (E) and magnetic (M) fields.
6
Q
What is an electromagnetic wave?
A
The combination of the electric field and the magnetic field waves.
7
Q
What is the relationship between the Electric and Magnetic fields in an E-M wave?
A
They are mutually at right angles to one another and to the direction of motion of the wave.
8
Q
Give examples of E-M waves.
A
Light wave
9
Q
How do electromagnetic waves travel?
A
At the speed of light.
10
Q
How do mechanical waves travel?
A
At a speed less than that of light.
11
Q
Are electromagnetic waves transverse or longitudinal?
A
Always transverse.
12
Q
What are some examples of electromagnetic waves arranged in order of increasing wave length?
A
Gamma rays
13
Q
What is the electromagnetic spectrum?
A
The whole range of electromagnetic waves.
14
Q
What is the speed of light in vacuum?
A
3.00 x 10⁸ ms⁻¹ and is represented by the letter c.
15
Q
What properties do electromagnetic waves exhibit?
A
Reflection
16
Q
How are wavelength (λ) and frequency (f) related?
A
λ = v/f or v = fλ.
17
Q
If v = c (the velocity of light)
A
how can the relationship between wavelength and frequency be written?
18
Q
What is the range of wavelengths for radio waves?
A
1 mm to a few kilometers.
19
Q
What are radio waves commonly used for?
A
Radio transmissions.
20
Q
What are X-rays used for in hospitals?
A
To make X-ray pictures or radiographs of the bones and internal organs of the body.
21
Q
What is the order of magnitude of the wavelengths of Gamma rays?
A
10⁻⁸ cm.
22
Q
What are Gamma rays used for in the medical field?
A
To sterilize medical supplies and to treat cancers and tumours.
23
Q
A certain radio station is assigned a frequency of 2000 KHz. Estimate the wavelength of its radio waves. (Take c = 3 x 10⁸ ms⁻¹).
A
λ = 150 m.
24
Q
Which of the following is not an electromagnetic radiation? A) X-ray B) Radio waves C) Sunlight D) Sound waves E) Infrared radiations.
A
D) Sound waves.
25
In which of the following groups are the radiations arranged in the increasing order of their wavelength? A) Radio waves
gamma rays
26
What is a field?
A region of space under the influence of some physical agency such as gravitation
27
What are the two classes of force fields described?
Scalar fields and Vector fields.
28
Give examples of Vector fields.
Gravitational
29
What are the students expected to be able to do after completing this chapter?
Calculate the gravitational force between two masses; Calculate the gravitational force between two planets; Explain the meaning of 'G' and show that 'g' is the force per unit mass on the earth's surface; Relate Kepler's Laws to the motion of the solar system; Distinguish between Natural and Artificial satellites; Explain how artificial satellites are launched; Explain the concept of Escape Velocity; Use the inverse square law to calculate the escape velocity of an object from the earth' gravitational field.
30
What are the two types of forces?
Contact forces and force fields.
31
Give examples of contact forces.
Pushing or pulling a wheelbarrow
32
Give examples of force fields.
Gravitational forces.
33
What is gravitational field?
A region or space around a mass in which the gravitational force of the mass can be felt.
34
What is gravitation?
The force of attraction exerted by a body on all other bodies in the universe.
35
What does Newton's law of universal gravitation state?
Every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them.
36
What is the formula for the magnitude of the gravitational force between two particles?
F = (Gm₁m₂)/r².
37
What is the value of the universal gravitational constant (G)?
G = 6.67 x 10⁻¹¹ Nm²kg⁻².
38
What type of forces is gravitational force?
A pair of forces
39
What does gravitational attraction keep in orbit?
The moon around the earth and the earth around the sun.
40
Are gravitational forces attractive or repulsive?
Attractive.
41
Two 5.0 kg spherical balls are placed so that their centres are 50.0 cm apart. What is the magnitude of the gravitational force between the two balls? (G = 6.67 x 10⁻¹¹ Nm²kg⁻²).
F = 6.67 x 10⁻⁹ N.
42
Determine the force of attraction between the sun (mₛ = 1.99 x 10³⁰ kg) and the earth (mₑ = 5.98 x 10²⁴ kg). Assume the sun is 1.50 x 10⁸ km from the earth.
F = 3.53 x 10²² N.
43
Calculate the gravitational force of attraction between the electron of a hydrogen atom and the proton when the electron orbits the proton at its average distance of 0.53 x 10⁻¹⁰ m. (Take mass of electron as 9 x 10⁻³¹ kg
and mass of proton as 1.67 x 10⁻²⁷ kg).
44
Calculate the gravitational force of attraction between two protons in a chemical compound. (Take the mass of a proton as 1.67 x 10⁻²⁷ kg and the distance between the protons in the chemical compound as 10⁻¹⁰ m).
F = 1.86 x 10⁻⁴⁴ N.
45
What is the formula for the gravitational force of attraction of the earth on any mass
m
46
What is the formula for the acceleration due to gravity (g) at the earth's surface?
g = (Gmₑ)/rₑ².
47
How can the mass of the earth (mₑ) be calculated?
mₑ = (grₑ²)/G.
48
Determine the mass of the earth if the radius of the earth is approximately 6.38 x 10⁶ m
G = 6.67 x 10⁻¹¹ Nm²kg⁻² and g = 9.80 ms⁻².
49
The radius of the moon is one-fourth
and its mass is one eighty-first that of the earth. If the acceleration due to gravity on the surface of the earth is 9.8 ms⁻²
50
What is Gravitational Potential (V) at a point?
The work done in taking unit mass from infinity to that point.
51
What is the formula for Gravitational Potential?
V = -Gm/r.
52
Find the Gravitational Potential at a point on the earth's surface. (Take mass of earth as 5.98 x 10²⁴ kg
its radius as 6.38 x 10⁶ m and G = 6.67 x 10⁻¹¹ Nm²kg⁻²).
53
What does the Solar System consist of?
The Sun and those celestial or heavenly bodied or objects that move around it
54
What are the objects that circle round the Sun known as?
Planets.
55
What are the names of the planets in order from the one nearest the Sun?
Mercury
56
What are the four smaller inner planets called and what are they primarily composed of?
Terrestrial planets; rock and metal.
57
What are the four outer planets called and what are they substantially more massive than?
Gas Giants.
58
What are the two largest planets mainly composed of?
Hydrogen and helium.
59
What is the principal component of the Solar System?
The Sun.
60
What is the Sun?
A giant star that contains over 99 percent of the Solar System's known Mass and dominates it gravitationally.
61
What is an important feature of the Sun?
It is a big ball of hot glowing gas and glows all the time emitting its own light and heat.
62
State Kepler's laws of planetary motion.
Law 1: The planets each travel along an ellipse with the Sun at one focus. Law 2: The line joining the Sun and the planets sweeps out equal areas in equal times. Law 3: The square of the period of revolution of the planets are proportional to the cubes of their mean distances from the Sun (T² ∝ r³).
63
What is a satellite?
Any object that moves round the earth or any body in space.
64
What are the two types of satellites?
Natural satellites and Artificial satellites.
65
What is a Natural Satellite or Moon?
A celestial body that orbits a planet or smaller body
66
Give an example of a natural satellite.
The moon.
67
What are artificial satellites?
Man made or human built objects orbiting the earth and other planets in the solar system.
68
What was the first artificial satellite and when was it launched?
Sputnik 1; 1957.
69
How are satellites launched into space?
They are first carried to the required height above the earth using rockets
70
What is the formula for the velocity (vₛ) of a satellite as it orbits round the earth?
vₛ = √(Gmₑ/rₑ).
71
What is escape velocity (vₑ)?
The minimum velocity required for an object to just escape or leave the gravitational influence or field of an astronomical body permanently.
72
What is the formula for escape velocity?
vₑ = √(2Gmₑ/R) or vₑ = √(2gR).
73
Calculate the escape velocity of a satellite from the earth's gravitational field. (g = 9.8 ms⁻²
radius of earth = 6.4 x 10⁶ m).
74
What is the relationship between the velocity of a satellite orbiting the earth and the escape velocity?
The escape velocity is √2 times the velocity of the satellite in orbit (vₑ = √2 vₛ).
75
What is the formula for the period of revolution (T) of a satellite?
T² = (4π²r³)/(Gmₑ).
76
What is the SI unit of Gravitational Potential?
Joule per kilogram (J/kg).
77
What is the shape of the orbits of planets around the Sun?
Elliptical
78
State Kepler's first law of planetary motion.
The planets each travel along an ellipse with the Sun at one focus.
79
State Kepler's second law of planetary motion.
The line joining the Sun and the planets sweeps out equal areas in equal times.
80
State Kepler's third law of planetary motion.
The square of the period of revolution of the planets is proportional to the cubes of their mean distances from the Sun (T² ∝ r³).
81
What are the terrestrial planets?
Mercury
82
What are the gas giant planets?
Jupiter
83
What is the most massive object in the solar system?
The Sun.
84
What is the source of the Sun's energy?
Nuclear fusion.
85
What type of waves are electromagnetic waves?
Transverse waves.
86
Do electromagnetic waves require a medium to travel?
No.
87
At what speed do electromagnetic waves travel in a vacuum?
3.00 x 10⁸ m/s.
88
What is the relationship between wavelength and frequency of an electromagnetic wave?
λ = c/f
89
Name the electromagnetic waves in order of increasing wavelength.
Gamma rays
90
Which type of electromagnetic wave has the highest penetrating power?
Gamma rays.
91
Which type of electromagnetic wave is used in radar?
Radio waves (short wavelength).
92
Which type of electromagnetic wave is used for sterilization?
Gamma rays.
93
State Newton's law of universal gravitation.
Every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them.
94
What is the formula for gravitational force between two masses?
F = (Gm₁m₂)/r².
95
What is the value of the universal gravitational constant (G)?
6.67 x 10⁻¹¹ Nm²kg⁻².
96
What is the relationship between the acceleration due to gravity (g) and the universal gravitational constant (G)?
g = (Gmₑ)/rₑ².
97
What is the formula for gravitational potential?
V = -Gm/r.
98
What is escape velocity?
The minimum velocity required for an object to escape the gravitational influence of an astronomical body.
99
What is the formula for escape velocity?
vₑ = √(2Gmₑ/R) or vₑ = √(2gR).
