http://www.ck12.org Chapter 4. Motion and Forces
A: When you pull on the band, it stretches but doesn’t break. The resistance you feel when you pull on it is elastic
force. The farther you stretch the band, the greater the resistance is. The resistance of the band to stretching is what
gives your muscles a workout. After you stop pulling on the band, it returns to its original shape, ready for the next
stretch.
Springs like the spring toy pictured in theFigure4.38 also have elastic force when they are stretched or compressed.
And like stretchy materials, they return to their original shape when the stretching or compressing force is released.
Springs are used in scales to measure weight. They also cushion the ride in a car.
FIGURE 4.38
Q: Can you think of other uses of springs?
A: Bedsprings provide springy support beneath a mattress. The spring in a door closer pulls the door shut. The
spring in a retractable ballpoint pen retracts the point of the pen. The spring in a pogo stick bounces the rider up off
the ground.
Summary
- Elasticity is the ability of a material to return to its original shape after being stretched or compressed. When
an elastic material is stretched or compressed, it exerts elastic force. This force increases the more the material
is stretched or compressed. - Elastic force has many uses, from hair scrunchies to bed springs.
Vocabulary
- elastic force: Counter force exerted by an elastic material when it is stretched or compressed.
- elasticity: Ability of a material to return to its original shape after being stretched or compressed.
Explore More
At the following URL, read the short article on elasticity and watch the earthquake animation. Then answer the
questions below.
http://www.scec.org/education/k12/learn/eq5.htm
- Which of the following have elastic properties?
a. pencils
b. rocks
c. rubber bands
d. all of the above - Materials with elastic properties have a point at which any additional force will permanently change the
object’s shape. That point is called the