Question 15
A spring of unextended
length 0.50 m is stretched by a force of 2.0 N to a new length of 0.90 m.
The variation of its
length with tension is as shown.
How much strain energy
is stored in the spring?
A 0.40 J B 0.80
J C 0.90
J D 1.8
J
Reference: Past Exam Paper – June 2007 Paper 1 Q19
Solution:
Answer:
A.
When the tension is 0 N (no
force is applied), the length of the spring is 0.50 m. This is the original
length of the spring.
A tension of 2.0 N causes
the spring to extend, from its original length, by (0.9 – 0.5) m.
Strain energy = Area under
tension-length graph
We need to consider the
area of the triangle formed.
Strain energy = ½ × (2.0 – 0) × (0.9 – 0.5) = 0.40 J
Note that strain (=
extension / original length) is NOT the same as strain energy.
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