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| # h3macasp1 | |
|
A force of 40 N. is required to hold a spring that has been stretched from its natural length of 10 cm to a length of 15 cm. How much work is done in stretching the spring from 15 cm to 18 cm? |
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| Strategy - the rule "Must have" of Mr.Zhang ® | ||
| Find the value of k ; | f(x)=kx | → (1) |
| And later find work done (w) from ; |  |
→ (2) |
| Solution |
Find k(constant of spring) from equation(1)
|
| 40 | = | 0.05k |
| k | = |
40
0.05
|
| = | 800 |
Thus, f(x)=800x
|
And the work done in stretching the spring from 15 cm to 18 cm is
|
Find work done(w) from equation(2)
|
| w | = |  |
| = |  |
|
| = | 400[(0.18)2-(0.15)2] | |
| = | 3.96 J |
| Ans. 3.96 J work is used for stretching the spring from 15 cm to 18 cm. |
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