(L14) S&F L4 - Fluid statics

Question 1

What is Archimede’s principle?

Answer 1

When a body is immersed in water, the fluid exerts an upwards force on the body equal to the weight force of fluid that is displaced by the body.

Question 2

What are the key points of Archimede’s principle?

Answer 2

• an object must be completely submerged in fluid
• volume of fluid displaed is equal to the volume of the object
• weight of th edisplaced fluid is equal to the upwards force on the submerged object

Question 3

What is result of Archimede’s principle?

Answer 3

A net upward force, called bouyancy force, is exerted on the submerged body by the sorrounding liquid

Question 4

What is bouyancy force equation?

Answer 4

Pf= density of liquid
V= volume of submerged portion of the body
g = accel due to gravity

Question 5

Body comes to rest in fluid equilbirum when:

Answer 5

bouyant force = total weight
mg = P,fVg

Question 6

m is mass of the submerged body.
What happens if
total weight > bouyant force

Answer 6

total weight > bouyant force
mg > P,fVg
body sinks

Question 7

m is mass of the submerged body.
what happens if
total weight < bouyant force

Answer 7

total weight <bouyany force
mg < P,fVg
body rises

Question 8

TRUE /FALSE ?
When the aluminium is submerged, but does not rest
on the base, the weight measured by the lower balance
increases …
1. by the weight of displaced fluid?

Answer 8

true

Question 9

TRUE /FALSE ?
When the aluminium is submerged, but does not rest
on the base, the weight measured by the lower balance
increases …
2. by an amount equivalent to the rise in
the water level?

Answer 9

true

Question 10

TRUE /FALSE ?
When the aluminium is submerged, but does not rest
on the base, the weight measured by the lower balance
increases …
3. by the weight of the aluminium?

Answer 10

FALSE

Question 11

TRUE /FALSE ?
When the aluminium is submerged, but does not rest
on the base, the weight measured by the lower balance
increases …
4. by the weight of water which has the
same volume as the aluminium?

Answer 11

true

Question 12

What is cohesion?

Answer 12

Attraction between like substances.

dancing with friendss :3

Question 13

What is adhesion?

Answer 13

Attraction between unlike substances

Question 14

What is surface tension good for

Answer 14

keeps bugs and needles and shit floating, on surface on water
-minimises surface area
-smallest surface area enclosing a volume is a sphere

Question 15

Why do we wash hands in warm soapy water?

Answer 15

less surface tension due to warmth, allows soap to get into crevices of our hands

Question 16

Equation for surface tension of bubbles?

Answer 16

Question 17

Force inside bubble equation?

Answer 17

Question 18

Larger the bubble, smaller the pressure inside the bubble

Answer 18

Smaller the bubble, larger the pressure inside the bubble.

Question 19

What happens when a small and a large bubble collide?

Answer 19

Due to the fact that small bubbles have higher pressure than big bubbles, the 2 bubbles conncect and the pressure of air flows from small bubble into bigger bubble.

Big bubble gets bigger and small bubble disappears

Question 20

What are alveoli?

Answer 20

Small sacs lined with surfactant.
Try get oxygen into bloodstream and CO2 out. Needs larger surface area to do this, but lots of bubbles and pressure into lungs.

Question 21

What is surface area of lungs?

Answer 21

About size of tennis court. 52-70m^2

Question 22

Why can we exhale with muscle contraction?

Answer 22

Because of surface tension of aveoli.

Question 23

What if Aveoli pressure too high?

Answer 23

Lungs difficult to inflate, due to water in lung or premature baby

Question 24

What if alveoli pressure too low?

Answer 24

emphysema. sacs combine to form larger sacs, difficulty exhaling as pressure in sacs reduced.

Question 25

What happens when you deep breathe.

Answer 25

When you inhale deeplly all sacs are open and avaliable, you can absorb more oxygen easier. Next breath introduced more oxygen than shallow breathing.

Question 26

What uses capillarity for life?

Answer 26

Plants use capillarity to draw nutrients into their stems.