BERNOULLI'S PRINCIPLE
SUBMARINE
A submarine makes use of the concept of buoyancy in order to float or sink in water. It contains special tanks called ballasts tanks that can contain either air or water. With air-filled tanks, the submarine sinks. The submarine carries cylinders of compressed air. When it is made to rise to the surface, compressed air is used to force the water out of the ballasts tanks.
![Picture](/uploads/3/0/6/1/30619403/3170864_orig.jpg)
Source : http://www.google.com.ph/imgres?imgurl=http://www.defencejobs.gov.au/navy/submariners/images/tech-submarine.jpg&imgrefurl=http://www.defencejobs.gov.au/navy/submariners/technology.aspx&h=404&w=942&tbnid=a5zQPypD_p1ufM:&zoom=1&docid=ji8LqrVeEL0hZM&ei=r50HVdH9McW2mwW934CwAw&tbm=isch&ved=0CD4QMygOMA4
Compare the weight of the submarine to the buoyant force of water while the (a) ballast tanks are empty; (b) ballast tanks are filled with water; (c) compressed air pushes the water out of the tank.
Answers:
a. In this figure, compared to the weight of the submarine, the buoyant force of water is somehow greater. Due to this, the submarine floats.
b. In this submarine, the ballast tanks are filled with water. The volume of the water filled in the ballast tanks adds up to the original mass of the submarine. With this, the mass of the submarine is greater than the buoyant force of the water, making the submarine submerge.
c. Compressed air pushes the water out of the tanks. Due to this, the water inside those ballast tanks that are supposed to help the submarine submerged is getting out. With this, we can say that the buoyant force of the water is slowly overwhelming the mass of the submarine making it emerge to the surface of the water.
a. In this figure, compared to the weight of the submarine, the buoyant force of water is somehow greater. Due to this, the submarine floats.
b. In this submarine, the ballast tanks are filled with water. The volume of the water filled in the ballast tanks adds up to the original mass of the submarine. With this, the mass of the submarine is greater than the buoyant force of the water, making the submarine submerge.
c. Compressed air pushes the water out of the tanks. Due to this, the water inside those ballast tanks that are supposed to help the submarine submerged is getting out. With this, we can say that the buoyant force of the water is slowly overwhelming the mass of the submarine making it emerge to the surface of the water.
BERNOULLI’S PRINCIPLE
Purpose:
Explain some situation using Bernoulli’s principle.
Materials:
Balloon
Hair blower
Drinking straw/cup of water
Beach ball or balloon/stand fan
Strip of paper
Explain some situation using Bernoulli’s principle.
Materials:
Balloon
Hair blower
Drinking straw/cup of water
Beach ball or balloon/stand fan
Strip of paper
![Picture](/uploads/3/0/6/1/30619403/4952155.gif?367)
Learning Station A: Kissing Ball
Blow at the middle of the two hanging balls. Observe what will happen.
Questions:
1. How did the two balls react? Use an illustration.
2. At which side of the two balls is the velocity of air greater?
3. What does the behaviour of the two balls suggests about the pressure between them and the pressure on either side?
Answers:
1. As we blew air at the middle of the two hanging balls, we have observed that they moved closer up to the point where the two ping pong balls touched each other.
2. Based on our experiment, the side of the balls which had the greater velocity of air are those located at the outer part of the two ping pong balls.
3. Bernoulli’s principle states that an increase in the velocity of the fluid results to a decrease in pressure. Relating to the activity conducted, we can somehow say that an increase in the air flow or velocity of the air results to a decrease in pressure. With this, we can say that before we started blowing air between the ping pong balls, the wind around the them are moving at a uniform speed making its velocity between and on either side of the ball equal. However, as we started blowing air in between of the balls, the velocity of the air in between the balls increased resulting to a decrease in pressure within that specific area. Due to this decrease in pressure, the balls moved closer to each other until they finally touched
Blow at the middle of the two hanging balls. Observe what will happen.
Questions:
1. How did the two balls react? Use an illustration.
2. At which side of the two balls is the velocity of air greater?
3. What does the behaviour of the two balls suggests about the pressure between them and the pressure on either side?
Answers:
1. As we blew air at the middle of the two hanging balls, we have observed that they moved closer up to the point where the two ping pong balls touched each other.
2. Based on our experiment, the side of the balls which had the greater velocity of air are those located at the outer part of the two ping pong balls.
3. Bernoulli’s principle states that an increase in the velocity of the fluid results to a decrease in pressure. Relating to the activity conducted, we can somehow say that an increase in the air flow or velocity of the air results to a decrease in pressure. With this, we can say that before we started blowing air between the ping pong balls, the wind around the them are moving at a uniform speed making its velocity between and on either side of the ball equal. However, as we started blowing air in between of the balls, the velocity of the air in between the balls increased resulting to a decrease in pressure within that specific area. Due to this decrease in pressure, the balls moved closer to each other until they finally touched
Source: JPEG : http://www.sciencebuddies.org/Files/3561/5/Aero_img071.gif
Learning Station B:
![Picture](/uploads/3/0/6/1/30619403/6864444.png?467)
Hold one edge of the strip of paper. Blow air above the loose end of the paper.
Questions:
1. How does the paper react as you blow at its bottom? Use an illustration for pressure directions.
2. How do you explain your observations?
Answers:
1. As we blow air at the bottom of the strip of paper, we observed that the strip of paper moved down.
2. This can be explained by the statement of the Bernoulli’s Principle. As air flow increases, pressure decreases. In the experiment, as we blew air at the bottom of the paper, an increase in the velocity of the air happened at the bottom of the paper which results to a decrease in pressure. So, the pressure below the paper becomes lesser and the pressure above the paper becomes greater. As a result, we have pushing force from above the paper that made the piece of paper move down.
Questions:
1. How does the paper react as you blow at its bottom? Use an illustration for pressure directions.
2. How do you explain your observations?
Answers:
1. As we blow air at the bottom of the strip of paper, we observed that the strip of paper moved down.
2. This can be explained by the statement of the Bernoulli’s Principle. As air flow increases, pressure decreases. In the experiment, as we blew air at the bottom of the paper, an increase in the velocity of the air happened at the bottom of the paper which results to a decrease in pressure. So, the pressure below the paper becomes lesser and the pressure above the paper becomes greater. As a result, we have pushing force from above the paper that made the piece of paper move down.
Source: JPEG : http://www.seykota.com/rm/delusions/delusions.htm
![Picture](/uploads/3/0/6/1/30619403/3536542_orig.png)
Learning Station: C
Switch on the hair blower and place the balloon above the blower.
Questions:
1. Why does the balloon/ball tend to stay within the air column? Use an illustration to show the direction of the NET PRESSURE.
2. Why does this happen?
Answers:
1. The ping pong ball tends to stay within the air column because the air in the center of the air stream moves a little faster than the air towards the edge.
2. The air at the sides of the air column rubs on the stationary air in the room and is slowed a little. Whenever the ball begins to drift off away from the centre, the faster air passing the ball will be on the side back towards the center. The faster air that produces less pressure in the inside of the air column and the slower air that produces larger pressure on the outside will cause the ping pong ball to return to the center of the air stream.
Switch on the hair blower and place the balloon above the blower.
Questions:
1. Why does the balloon/ball tend to stay within the air column? Use an illustration to show the direction of the NET PRESSURE.
2. Why does this happen?
Answers:
1. The ping pong ball tends to stay within the air column because the air in the center of the air stream moves a little faster than the air towards the edge.
2. The air at the sides of the air column rubs on the stationary air in the room and is slowed a little. Whenever the ball begins to drift off away from the centre, the faster air passing the ball will be on the side back towards the center. The faster air that produces less pressure in the inside of the air column and the slower air that produces larger pressure on the outside will cause the ping pong ball to return to the center of the air stream.
Source : JPEG :
http://rivertoncats.com/?page_id=72
http://rivertoncats.com/?page_id=72
![Picture](/uploads/3/0/6/1/30619403/6219351_orig.jpg)
Learning Station: D
Blow air through the vertical straw
What did you observe as you blow air through the vertical straw?
When we blew air through the vertical straw, we observed that the water somehow moved up.
How do you explain your observations?
As air was blown into the vertical straw, the pressure decreased due to the change in the air flow. With the decrease of pressure inside the straw, this makes the pressure on the surface of the water relatively greater which causes the water to rise up to the surface of the water.
Blow air through the vertical straw
What did you observe as you blow air through the vertical straw?
When we blew air through the vertical straw, we observed that the water somehow moved up.
How do you explain your observations?
As air was blown into the vertical straw, the pressure decreased due to the change in the air flow. With the decrease of pressure inside the straw, this makes the pressure on the surface of the water relatively greater which causes the water to rise up to the surface of the water.
Source : JPEG : Source: http://lhs.loswego.k12.or.us/z-alts/ Conceptual%20Physics/Unit%206%20Pressure/ 05Energy%20and%20Pressure%20Review%20Answers.htm