Upthrust and Stoke's Law

A ball of volume V_b and density p_b is released in a volume V_l of liquid with density p_l. The upthrust on the ball is given by

• V_b p_b g

• V_b p_l g

• V_l p_b g

• V_l p_l g

Q and R are drops of two different fluids which have been placed on one end of the tile which is tilted. The drops spread down the tile. Which could be a correct explanation for the different lengths shown?

• R has a greater viscosity than Q

• R has a greater density than !

• R has a greater temperature than Q

• All of the above

In the expression...

 $F=6\pi\eta rv$  

•  $\eta$  represents density and  $\nu$  represents viscosity

• r represents radius and  $\eta$  represents density

• r represents radius and  $\nu$  represents viscosity

•  $\eta$  represents viscosity and  $\nu$  represents velocity

What is meant by the term viscosity?

A small metal ball is dropped into a cylinder of oil. The time taken for the ball to fall to the bottom is recorded. Which changes to the ball would result in the greatest decrease in the time taken to reach the bottom?

• Smaller mass and smaller diameter

• Smaller mass and greater diameter

• Greater mass and smaller diameter

• Greater mass and greater diameter

A ball bearing is dropped through a liquid and its terminal velocity measure. The experiment is repeated at a different temperature. Which answer correctly describes this second experiment?

• Lower temperature: greater viscosity and faster velocity

• Lower temperature: greater viscosity and slower velocity

• Higher temperature: greater viscosity and slower velocity

• Higher temperature: smaller viscosity and slower velocity

The table shows the diameters of different particles in soil. If soil is added to water, which particles will settle on the bottom first (assuming all particles are the same density)?

• Clay

• Silt

• Sand

• Fine Pebbles

• Coarse Pebbles

Explain why the coarse pebbles hit the bottom first.

As a balloon rises through the air, the density of the surrounding air decreases. Why does this limit the height the balloon can reach?

The surface of a golf ball is covered in small dimples. These dimples enable the ball to travel a greater distance. Which of the statements is true?

• The dimples result in only turbulent flow

• The dimples result in only laminar flow

• The dimples reduce drag

• The dimples increase drag