Page 130 - Physics

Physics for Secondary Schools

The graph of tension against extension is part between points B and C, the spring
shown in Figure 6.4. undergoes plastic deformation, whereby
it remains deformed even after the load
is removed. The spring will continue to
increase in length until a certain maximum
6
C tension is reached. Beyond this tension,
A
Tension (N) 4 3 the spring will fi nally break. In the elastic
5
B
region, the ratio of the applied force (F)
to the distance stretched (e) is called the

2 elastic force constant, k. Hence, k = F .
1 The SI unit of k is N/m. e

O 1 2 3 4 5 6 7 8
Extension (cm) Exercise 6.1

1. A force of 40 N is applied to the spring
Figure 6.4: Relationship between tension and
extension of a stretched spring with a spring constant of 100 N/m.
What is the resulting displacement
Certain observations can be made from the of the spring?
graph in Figure 6.4. For the portion between 2. A rubber band has an original length
O and A, the tension (force) is directly of 20 cm and is stretched to a length
proportional to the extension of the spring. of 25 cm. What is the percentage
This is in accordance with Hooke’s law, change in length of the rubber band?
which explains the relationship between
the force applied on an elastic material and 3. A spring has a spring constant of
the extension produced. 80 N/m. If the spring is compressed
by 30 cm, what is the resulting force
applied to the spring?
Hooke’s law states that: “Provided
the elastic limit is not exceeded, the
extension is directly proportional to the Applications of elasticity in daily life
force applied”. Elasticity has a variety of applications
at home, in transport, and industry. At
The elastic limit is the maximum point home, the applications of elasticity can
beyond which the material cannot return be observed in:
to its original shape when the deformation
force is removed. If the elastic limit is (a) rubber gaskets that seal the refrigerator
door;
exceeded the material experiences plastic
deformation. From the graph, in Figure (b) clothing;
6.4, point B is the elastic limit and the (c) springs in furnitures;

124
Student’s Book Form One

Physics Form 1 Final.indd 124 16/10/2024 20:57