Simple and new working models on science topics?

Answer 1

that work together to

allow the bones to move

in different directions).

For example, your forearm can rotate because

the two bones of your

forearm (the ulna and

radius) are connected by

a pivot joint. These bones

also connect to the humerus bone of the upper

arm by a hinge joint, allowing the forearm to

be raised. The compound joints in your neck

allow your head to move in different directions, including from side to side, nodding up

and down, as well as in a circular motion.

Movable joints need a lubricant (a substance that reduces friction between materials

in contact with each other) and cushioning

(soft padding material) that prevents the bones

from grinding against each other. The ends of

the bones in these joints are covered with cartilage, which acts as a cushion between the

bones. These joints also contain a special fluid

called synovial fluid, which is a lubricant.

ACTIVITY: MOVABLE

Purpose

To make a ball-and-socket joint model.

Material

2-quart (2-L) bowl

1 pound (454 g) instant papier-mâché

(air-dry clay also works well)

2-cup (500-mL) measuring cup

tap water

1-gallon (4-L) resealable plastic bag

craft stick

waxed paper

Procedure

1. In the bowl, mix papier-mâché and water as

indicated on the package.

2. Separate an apple-size piece of papiermâché and place the remaining papiermâché in the resealable bag. Store the bag

in a refrigerator until needed.

3. Break the apple-size piece of papier-mâché

in half. Form one of the pieces into a bowl

shape. Set the bowl on a piece of waxed

paper.

4. Shape the remaining piece of

papier-mâché into a ball.

5. Stick about 1 inch (2.5 cm) of the

craft stick into the ball. Squeeze

the papier-mâché around the

stick to secure it.

6. Cover the end of the ball with

waxed paper. Then stand the

waxed paper-covered ball

inside the papier-mâché

bowl. Reshape the bowl so

that the sides of the bowl

cover most of the ball.

7. With the ball inside the bowl,

allow the bowl and ball to sit

undisturbed overnight. They will

be partially dry in the morning.

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Gliding Joint

p02.qxd 6/1/04 11:28 AM Page 368. Touching the ball and not the stick, carefully rotate the ball to slightly enlarge the

size of the bowl so that the ball has room

to move and be removed from the bowl.

9. Allow the bowl and ball to sit undisturbed

until they dry. This could take two or

more days.

10. When the papier-mâché pieces are dry,

remove the waxed paper, then hold the

stick and move the ball around inside the

bowl.

Results

You have made a model of a ball-and-socket

joint.

Why?

In a ball-and-socket joint, one bone is movable

and the other is fixed. The movable bone has a

rounded end, represented by the ball-shaped

papier-mâché model. This rounded end fits into

a socket in a fixed bone, represented by the

bowl-shaped papier-mâché model. The bone

with the rounded end can move in all directions, including rotating around. In the shoulder joint, the rounded end of the humerus bone

of the upper arm fits into a bowl-shaped

socket in the scapula (shoulder

bone). You can rotate your arm in a

360° vertical circle.

ON YOUR OWN

1. Use papier-mâché to

make models of a

hinge joint, a pivot

joint, and a gliding

joint like the ones

shown here.

2. Design a way to display your models. One

way is to stand the joint models in front of a

three-paneled backboard. (See Appendix 1

for instructions on making the backboard.)

Information sheets about each model can be