Page 19 - 新思维科学学生用书4 样章

1 Living Things

Think like a scientist

Make a model of arm muscles
You will make a model to show how the muscles of the arms work in pairs.

You will need:
a piece of thick card, two elastic bands (one longer than the other),

scissors, paper fastener (split pin), stapler and staples, a ruler, a

piece of sticky tack or modelling clay

• Cut two equal lengths of card about 20 cm long.

card lengths
• For each piece of card, make a hole about 5 cm away card lengths
from one end using the point of the scissors. Place a piece of

sticky tack or plasticine behind the card to push the scissors into.

Be careful when making the hole with the scissors. You will need
to push harder because the card is thick and your hand could slip
split pin
and cut yourself. Take care with the sharp point of the split pin. split pin

• Put the card pieces on top of each other with the

holes lined up. Push the paper fastener through the short staple
staple
long elastic
elastic
holes to join the two pieces of card. This is your arm. short elastic long elastic
band
band
band
• Staple the longer elastic band to the inside of the band
upper and lower ‘bones’ of the card arm. split pin
split pin
• Staple the shorter elastic band to the outside of the upper and lower
‘bones’ of the card arm. The elastic bands should be tight but not pulling.

Questions

1 What happens to the card arm when you pull on the longer elastic band?

2 What happens to the card arm when you pull on the shorter elastic band?

3 Explain how the two elastic bands act like muscles in the body that

lift and lower the arm.
4 a In what ways is your model the same as your arm muscles?

b In what ways is your model different to your arm muscles?

18