Question

the mass of a uniform copper bar varies directly as it's length.if a bar 40cm long has a mass approximately 420g, find the mass of a bar 136cm long

Answer 1

Here, we are given that Mass varies directly as length.

So, we can say that Mass of the Rod is directly proportional to length.

$Mass \, \propto \, Length \\ \\ \\ \implies m \propto l \\ \\ \\ \text{We can write} \\ \\ \\ m = k l$

Where k is a constant.

Mass of a 40 cm long bar is 420 grams.

We can write:

$420 = k \times 40 \\ \\ \\ \implies k = \frac{420}{40} \\ \\ \\ \implies k = \frac{21}{2}$

Our equation becomes:

$m = \frac{21}{2} l$

Now, we have to find mass of a 136 cm long bar.


$m = \frac{21}{2} l \\ \\ \\ \implies m = \frac{21}{2} \times 136 \\ \\ \\ \implies \boxed{m = 1428\, \, grams}$

Thus, Mass of the bar is 1428 grams.



Hope it helps
Purva
Brainly Community

Answer 2

Answer:

Step-by-step explanation:

Let the mass be x

Mass=420,x

Length=40,136

So using unitary method:

40x=420×136

X=420×136/40

X=1428g

Therefore,the mass of the bar 136cm long is 1428g