Question

Lewis has a copper pipe with a length of 150 cm and a mass of 800 grams. He cuts a piece of the copper pipe with a length of 90 cm. How do you work out the mass of this piece of copper pipe?

Answer 1

I got `477g`

Explanation:

I would consider the Linear Density of the pipe as:

`delta="Linear Density"="mass"/"length"`

or:

`delta=800/150=5.3g/(cm)`

When you cut it you are left with `90cm` of pipe but with the same linear density `delta` so we can write:

`5.3=m/90`

or

`m=5.3*90=477g`

Answer 2

The `"90 cm"` piece of the pipe will have a mass of `"480 g"`.

Explanation:

From the question, we get a relationship of equality between the length and mass of the pipe.

`"150 cm = 800 g"`

There are two conversion factors as shown below.

`"150 cm"/"800 g"` or `"800 g"/"150 cm"`

Multiply `"90 cm"` by the conversion factor that cancels cm.

`90color(red)cancel(color(black)("cm"))xx(800"g")/(150color(red)cancel(color(black)("cm")))="480 g"`