Question

The lengths of two rods are recorded as l₁ = (25.2 ± 0.1) cm and l₂ = (16.8 ± 0.1) cm. Find their combined length.

Answer 1

Answer:

l1+l2=25.2+16.8= 42cm

delta l1+delta l2=0.1+0.1= 0.2

combined length=(42+.2)cm

(42-.2)cm

Answer 2

The lengths of two rods are recorded as l₁ = (25.2 ± 0.1) cm and l₂ = (16.8 ± 0.1)cm.

then, we have to find their combined length.

concept : if two same physical quantities x and y are represented as

x = a ± ∆a , y = b ± ∆b respectively.

then, sum of x and y = (a + b) ± (∆a + ∆b)

here, l₁ = (25.2 ± 0.1) cm

and l₂ = (16.8 ± 0.1) cm

so, combined length = l₁ + l₂

= (25.2 + 16.8) ± (0.1 + 0.1)

= (42 ± 0.2) cm

hence, combined length = (42 ± 0.2) cm