A. We can write the formula as:
l = k(mg/A)
where k is the constant of proportionality. To find k, we plug in the given values:
18 = k(4*0.4/1)
18 = k(1.6)
k = 11.25
Therefore, the formula connecting l, m and A is:
l = 11.25(mg/A)
B. We are given m = 3g and A = 0.5² = 0.25cm². Plugging in these values into the formula, we get:
l = 11.25(3*0.25/0.25)
l = 33.75
Therefore, the length of the pencil is 33.75 cm.
The length of a pencil lcm, varies directly with it's mass, mg, and inversely with it's area of cross-section, Acm². When m=4 and A=0•4, I=18.
A. Find the formula connecting l, m and A
B. Hence find the length of a pencil which has a mass of 3g and a cross-sectional area of 0•5²
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