physics Density - Grade 9

In the photo shown, there is a person floating in the water of the Dead Sea. Why does this person not sink?

• He is not a very heavy person

• The density of the saltwater is greater than the man's density.

• His body is more dense than the density of the saltwater

• This person must be lying on a submerged airbed

Which of the following metals will sink in a basin of mercury whose density is 13.6 g/cm³?

•  Iron of density 7.9 g/cm³

•   Uranium of density 19.5 g/cm³

• Aluminium of density 2.7 g/cm³

•  Lead of density 11.3 g/cm³

If V = volume, D = density and M = mass of an object, then which one of the following relationships is correct?

•  M = D × V

• D = M × V

• V = M × D

• M = D ÷ V

Which one of the following would you NOT use to get the density of a liquid?

•   Balance

• Measuring cylinder

• Beaker

• Vernier callipers

The density of aluminium is 2.7 grams per centimetre cubed.
What mass will a volume of 200 cm³ of aluminium have?

• 54 grams

• 540 grams

• 5.4 grams

• 0.054 grams

Which one of the following statements is INCORRECT?

• A solid object floats in a liquid if it is less dense than the liquid.

•  A steel ship will sink in seawater because its density is greater than the density of the seawater.

• Different types of wood (e.g. mahogany, pine, cork etc.), all of the same shape will all float at different depths in water.

• The density of a submarine will determine if it floats submerged, or if it sinks in the water.

If copper floats on mercury, and gold sinks in mercury, then which one of the following statements is TRUE?

• 1.  Mercury is the least dense of the three metals

• 1.  Mercury is denser than gold

• 1. Copper is less dense than gold.

• 1.  Copper is more dense than mercury

Study the chart showing the densities of different metals.

• 5,25 gram

• 5,1 gram

• 6,5 gram

• 0,5 gram

Which of the following substances is the least dense?

• 1.  Carbon dioxide

• 1.  Steam

• 1. Helium

• 1. Water

Why did the balloon come back down to the ground?

• The air around it pushed it down.

• The air inside cooled and became more dense forcing the balloon to descend.

• The air inside the balloon heated up and the air was too hot to rise. 

• The balloon may have had a hole in it.