Question

1. The amount of extension in an elastic spring varies directly as the weight hung on it. If a weight of 150 gm produces an extension of 2.9 cm, then what weight would produce an extension of 17.4 cm

Answer 1

900 g

Explanation:

let e be extension and w be weight

given e varies directly as w then the equation relating them is

e = kw ← k is the constant of variation

to find k use the condition w = 150 , e = 2.9 , then

2.9 = 150k ( divide both sides by 150 )

`(2.9)/(150)` = k , that is

k =
`(29)/(1500)`

e =
`(29)/(1500)` w ← equation of variation

when e = 17.4 , then

17.4 =
`(29)/(1500)` w ( multiply both sides by 1500 )

26100 = 29w ( divide both sides by 29 )

900 = w