Question

aluminum is used to make airplanes and cast iron is used in weight lifting equipment.
Explain why the densities of these metals make them useful for these purposes.

Answer 1

can somebody help me with this physical science please

Answer 2

Aluminum is a relatively low density metal with good strength characteristics. Airplanes need to overcome gravity to get up in the air. The lighter an airplane is, the less force it has to exert which makes it fly either faster or more efficiently.

If you want your plane to go faster or fly farther (you do, that's how you make more money with it), you want to select a low density high strength material like aluminum. Recently, manufacturers have started moving towards carbon fiber as it can be even stronger and lighter than the traditionally used aluminum alloys.

Now for weight lifting equipment, you want the exact opposite. Weight lifters get a better workout by picking up heavier things. But at the same time, they don't want to carry around things that are too big. Carrying 100 lbs of lead is easier than 100lbs of feathers because its hard to carry all the feathers at once. That is to say, a denser material, such as cast iron, is an effective choice for weight lifting equipment. You can have heavy weights without taking up too much space.

Remember to always think of what the intended purpose/objective is, and what material property is related to that purpose