Question

How long will the spring be when I put $7$ kilograms of weight on it?

• A. $14.5$ cm
• B. $15.5$ cm
• C. $16.5$ cm
• D. None of these

Answer 1

Answer: (B)

$15.5$ cm

From the given table weight for 6.5cm length weight is 1kg

Let l represent as y and w represent as x

Hence in coordinates we can write as $(1,6.5)$ and from second column of table second point is $(2,8)$

Hence work out equation from $(1,6.5)$ and $(2,8)$

$y-6.5=\frac{8-6.5}{2-1}(x-1)$

$y-6.5=\frac{1.5}{1}(x-1)$

$y-6.5=1.5x-1.5$

$y=1.5x+5$

Since y as l and x as w

$l=1.5w+5$

For 7 kg weight putting $w=7$ in above equation

$l=1.5\times 7+5$

$l=10.5+5$

$l=15.5cm$