Q&A

1. A motion of 1 1/4 vibrations is shown as the following successive motion...
• A-B-C-B-A-B
2. Which part is considered as the amplitude?
• 
  
3. If the same pendulum moves as a-b-c-b-a-b, its motion performs…
• A-B-C-B-A-B-C
4. The number of vibrations performed in every second is…
• The frequency
5. If 120 vibrations happen in one minute, the correct statement is...
• its period is 1/2 seconds
6. A period of a swing is 5 seconds in every minute, the pendulum will perform...
• 12 swings
7. If in 1 over 4 seconds the ruler moves in the B-C-B-A pattern, period of the vibration made by the ruler is…
• 3/4 seconds
8. If the frequency of a vibration is 350 Hz, the period of such a vibration is...
• 1/350 seconds
9. A pendulum performs swings with a frequency 40 Hz. The number of vibrations that it can make within 3 minutes is…
• 7,200
10. If 18,000 waves are performed in 4 minutes, then…
• the period of the wave is 1/75 seconds
11. 1 1.2 wave --> t= 0.5 s What is the frequency of the wave?
• 3 Hz
12. The frequency of a wave is 300 Hz. If the velocity of the wave is 900 m/s, the wavelength is…
• 3 m
13. The length of two transverse waves is 2 m and 2x the wavelength is 3 m.
• The following statements are related to that statement.
• 1. The amplitude of the wave is 4 m.
• 2. The wavelength is 5 m.
• 3. The velocity of the wave is 100 m/s
• If the frequency of the wave is 100 Hz, the correct statement(s) are/is 
• only 3
14. If the vibration direction is perpendicular to the direction of wave propagation, it means that the wave is a...
• transverse wave
15. The velocity of a wave is 150 m/s and its frequency is 300 Hz. The wavelength is...
• 0.5 m
16.  Sound propagates in the air with a speed 600 m/s. If the frequency of the keynote a is 150 Hz, then the wavelength is…
• 4 m

Q&A

1. A spring-mass system vibrates exactly 10 times per second. Find its period and its frequency. 
• f = 10/1 = 10Hz
• T = 1/10 = 0.1
2. A pendulum swings with a period of 0.20 seconds. 
• What is its frequency?
• f = 1/0.20 = 5Hz
• How many times does it pass the lowest point on its path in 1.0 second? in 7.0 seconds? 
• 1 second = 5 times          14 times = 70 times
3. A spring-mass system completes 20.0 vibrations in 5.0 seconds, with a 2.0 cm amplitude. 
• Find its frequency and its period. 
• f = 20/4 = 5Hz
• T = 1/5 = 0.2
• The same mass is pulled 5.0 cm away from the equilibrium position, then released. What will the period, the frequency, and the amplitude be? 
4. A pendulum completes 30.0 oscillations per minute. Find its frequency, its period, and its length. 
• f = 30/60 = 0.5Hz
• T = 60/30 = 2s
• A = 2/time = 30
5. A clown is rocking on a rocking chair in the dark. His glowing red nose moves back and forth a distance of 0.42 m exactly 30 times a minute, in a simple harmonic motion. 
• What is the amplitude of this motion? 
• A = 0.42/2 = 0.21m
• What is the period of this motion? 
• 60/30 = 2s
• What is the frequency of this motion? 
• 30/60 = 0.5Hz
• The top of the clown’s hat contains a small light bulb that shines a narrow light beam. The beam makes a spot on the wall that goes back and forth between two dots placed 1.00 m apart as the clown rocks. What are the amplitude, period, and frequency of the spot’s motion? 
6. A turning fork has a frequency of 256 Hz. The wavelength of the sound produced by the fork is 1.3 meters. Calculate the velocity of the waves.
• v = wavelength x f           1.3m x 256Hz = 332.8 m/s
7. Green light has a wavelength of 5.2 x 10-7 m and travels through the air at speed of 3 x 108 m/s. Calculate the period and the frequency of this green light waves. 
8. Radio waves travel at the speed of light 3.00  108 m/s. An amateur radio system can receive radio signals at frequencies between 8.00 MHz and 1.20 MHz. What is the range of the wavelengths this system can receive? 

Velocity of a Wave

Velocity

• The rate on how fast a wave propagates
• Formulas


• λ x f *wavelength x frequency*
• λ/t *wavelength / period*

Examples

If a car is moving at 50 km in an hour, what is the velocity?

Answer:

v = 50/60

v = 0.84

If a wave has a frequency of 10 Hz, and its wavelength is 3 cm, what is the velocity?

Answer:

v = λ x f

v = 10 x 3

v = 30 m/s

Waves

Definition

A wave is a vibration that travels through a distance which increases along a medium.

Types of Wave

• Mechanical Wave

• A wave that needs a medium in order to propagate is known as a mechanical wave.
• Example: Ocean wave

• Electromagnetic Wave
• An electromagnetic wave is a wave that does not need a medium or any media to propagate.
• Example: Microwave radiation

Elements of a Wave

• Transverse Wave
• A transverse wave is always in the form of a peak.
• Longitudinal Wave
• A longitudinal wave consist of a compression-expansion pattern throughout the wave.

Wavelength

• The distance of one wave

Frequency, Period and Amplitude

Frequency

The number of vibrations an object executes in one second is known as frequency. Hertz (Hz) is used as the unit of measurement for this phenomenon. The formula to this scientific meaning is F = n/t. *n = vibration , t = time*

Example

If a pendulum performs 360 swings in 2 minutes, what is the frequency?
Answer:
F = n/t
F = 360/120
F = 3 Hz




Period
The time it takes an object to accomplish one vibration is called period. The formula to find the period is T = t/n or T = 1/f. *t = time , n = vibration*

Example
What is the period if an object performs 60 vibrations in 30 seconds?
Answer:
T = t/n
T = 30/60
T = 0.5 seconds

Amplitude
The amplitude of an object is the farthest position from its balance position. Therefore, the formula to calculate amplitude is A = d/f. *d = distance , f = frequency*

Vibration

What is vibration?
The continuous back and forth movement in which an object imitates is known as vibration.

Examples

• A running motor

• The strumming of guitar strings        
• A car traveling over a rough path
• A pendulum

Pendulum as an Example

• 1

• 1 1/2

• 2

• 2 1/4

• 2 3/4

Conservation of Mechanical Energy

Mechanical Energy
The energy that is associated with motion is known as mechanical energy. There are two forms of mechanical energy, otherwise known as kinetic and potential energy.

Examples:

• A flying aircraft
• A moving vehicle

Kinetic Energy
Kinetic Energy occurs when the object is in motion.

Examples:

• A moving bicycle

Potential Energy
Potential Energy occurs when the object is not in communication with the ground. 

Examples:

• A flying kite
• A hanging swing

Formulas

• Kinetic Energy
• 1/2 x V2
• Potential Energy
• m x g x h

Conservation of Energy
Energy that can't be made or destroyed but can only be transformed is known as conservation of energy. 

More About Sources of Energy

• Fossil fuels are considered as a source of energy which is not renewable. Why is it so?

• The reason why fossil fuels are considered as nonrenewable energy is because it takes thousands of years to be produced.

• What happens if the fuel consumption is not spared?

• If  fuel is not spared between regions, the prices will increase in the areas that don’t posses as much fuel.

• Write down the dangerous issues of having a nuclear power plant.

• Nuclear power plants are extremely dangerous. They can easily leak at any point in time. For instance, in the year 2011, Fukushima Daiichi, Japan was faced against a tsunami, which caused a nuclear power plant to leak radioactive waste into the sea.

• According to your opinion, in order to produce electrical energy, what is the best energy that fits with the current situation and is pollution free?

• In my opinion, I think that using solar panels is the best method in order to create electrical energy. This system is entirely pollution free and can be very helpful in areas of long sun hours such as Jakarta.

• Write your suggestions in order to produce a very high temperature, so that a large amount of electricity can be generated from the use of seawater.
• Fusion energy can be used to help generate electricity from the use of seawater.

Sources of Energy

Sources of energy can be composed of food, sunrays, and waterfalls.

There are two types of sources of energy: the first being renewable energy and the second nonrenewable.

Renewable Energy:

·      Wind Energy

o   Windmills are used to generate electricity for the many purposes needed. However, the amount of energy produced is relatively small and size of a windmill is quite large.

·      Waterfall Energy

o   Using turbines is another way to produce energy. Water is used to rotate the turbine henceforth creating energy.

·      Solar Energy

o   With the help of solar panels, it is now possible to create solar energy. Solar panels are usually placed on the roof of a house to collect solar energy from the sun.

·      Nuclear Energy

o   The splitting of an atomic nucleus is known as fission. This process can generate a powerful source of energy.

·      Tidal Energy

o   Tidal power from rivers is used to generate another source of energy.

·      Geothermal Energy

o   The steam that comes from a geyser can be of help when producing energy.

·      Biomass Energy

o   The energy that comes from plants or animals is called biomass energy. Alcohol can be made from plants, which then can be used for fuel.

Nonrenewable Energy:

·      Fossil Fuel

o   Examples: Charcoal, gasoline

Work Assignment

A tugboat pulls a ship with a constant force of 5000 N, causing the ship to move through a harbor. How much work does the tugboat do on the ship if each moves a distance of 3 km?

Answer:
W= F x D

= 5000 N x 3000 m

= 15 000 000 J

= 15 MJ

A husky dog does 20 kJ of work as he pulls a sleigh with a force of 340 N. Through what distance does he pull it?

Answer:

W= F x D

W = 20 000 = 340 x D

D = 20.000/ 340

= 58.8 m

What is the weight of a mass of 100 kg? Find the work done in raising a mass of 100 kg through a vertical height of 60 m.

Answer:

W = F x D

= 1000 x 60

= 60 000 J

= 60 KJ

Carlos does a chin-up in gym class and raises himself 0.8 m. If Carlos has a mass of 62 kg, how much work does he accomplish?

Answer:

W = F x D

= 620 x 0.8

= 490 J

A girl pushes her little brother on his sled with a force of 300 N for 750. m. How much work is this if the force of friction acting on the sled is (a) 200 N, (b) 300 N?

Answer:

a. W= (F1-F2) x D

    = (300 – 200) x 750

    = 75 000 J

    = 75 KJ

b. W= (F1-F2) x D

    = (300-300) x 750

    = 0

Energy

What is energy?

Energy is the enforcement that allows work to occur. Therefore, whenever there is work, there is energy.

There are a variety of diverse forms of energy. The forms of energy are chemical energy, thermal energy, sound energy, light energy, electrical energy, and mechanical energy.

-       Chemical energy is the energy is an energy contained within food, your body, and fuel.

o   Example: The energy contained in food

-       Thermal energy is the energy associated with the random motion of particles.

o   Example: Rubbing your hands together to create heat

-       Sound energy is the energy produced by the radiation of air particles around a sound source.

o   Example: A person playing the clarinet

-       Light energy is the energy produced by the radiation of electromagnetic waves.

o   Example: Flashlight

-       Electrical energy is the energy produced by electric charges that move through cables.

o   Example: Laptop charger

-       Nuclear energy is the energy released from the reaction of the nucleus of radioactive matters.

o   Example: Nuclear bomb

-       Mechanical energy is the energy associated with motion.

o   Potential energy is in occurrence when the object is not touching the surface.

§  Example: Chandelier

o   Kinetic energy is present when an object is in motion.

§  Example: A moving car