Buoyancy

A ball of volume 𝑉_b and density 𝜌_b is released in a

volume 𝑉₁ of liquid with density 𝜌₁. The upthrust on

the ball is given by ____.

• 𝑉_b 𝜌_b 𝑔

• 𝑉_b 𝜌₁ 𝑔

• 𝑉₁ 𝜌_b 𝑔

• 𝑉₁ 𝜌₁ 𝑔

A block of metal is thrown into a lake. What

happens to the buoyant force as it sinks deeper in the

water?

• Increases

• Decreases

• Stay the same

• increase and then decrease

What is the buoyant force on a 20 𝑘𝑔 box that

displaces 4 𝑚³ of water?

• 800N

• 40000N

• 4000N

• 20000N

Three equal sized balls of volume 10𝑐𝑚³ are

made of cork, aluminum and lead with their

respective masses of 2𝑔, 27𝑔 𝑎𝑛𝑑 113𝑔. They are

submerged in water as shown in the figure.

Which of the statements below is incorrect?

• The cork would rise up and float

• Buoyant force on lead is the largest

• Lead and aluminum would both sink

• Each ball would displace the same

  volume of water

A 5 N stone is dropped in a lake and it sinks.

Which of the relationships below is true for the

buoyant force on the stone?

• 𝐹_b = 0

• 𝐹_b = 5

• 𝐹_b is greater than 5

• 𝐹_b is less than 5

What is the magnitude of the buoyant force on a

20 𝑁 ball that is floating in a liquid of density

800𝑘𝑔/𝑚³ .

• 20N

• 40N

• 80N

• 800N

Find the tension in the wire supporting a

120 𝑘𝑔 object of volume 0.1𝑚³ submerged in water

as shown in the figure below.

• 200N

• 400N

• 880N

• 2200N

An object will be in equilibrium in a fluid if __.

• the weight of an object is greater than the

  buoyant force

• the weight of an object is less than the

  buoyant force

• the weight of an object is equal to the

  buoyant force

• the weight doesn't affect if an object

  sinks, only its state of matter

Which of the following statements is/are correct

about neutral buoyancy?

• The object is lighter than the fluid it displaces

• The object is denser than the fluid it displaces

• The object’s weight is equal to the fluid it

  displaces

What is the magnitude of net force acting on the object in water if mass of object is 20Kg and buoynat force is 40N.

• 240N

• 20N

• 160N

• 200N