Помогите задать к тексту 2 специальных и 1 общий вопрос:
When I choose a material for a bike frame, I have to
think about the properties of the material. How elastic
Ís it? If you bend or stretch it, will it go back to its
original shape? If it does, it has high elasticity. How
strong is it? There are two kinds of strength. The first is
how much force you need to bend it to a point where it
can't go back to its original shape. The second is the
amount offorce you need to break it.
Steel is the least expensive choice. There's a wide range
of standard gauge tubes available. It's strong and it has
good elasticity but it's heavy.
Aluminium is lÍght and strong but it,s flexible. The
more it bends, the quicker Ít breaks. So aluminium bike
frames use large diameter tubes. That limits the
amount of bending.
Titanium has a great strength.to.weight ratÍo. It,s got
good elasticity so when it bends it tends to return to its
original shape. It's corrosion-resistant so you don,t
need to paint it. But it's expensive
- fifteen times the price of steel!
The professÍonals use carbon
fibre. It's very light and it's very
strong. You can shape it any way
you like. But carbon-fibre
frames are hand-made
so they're very
expensive