Calculate the elongation produced in each of the spring combinations:

Explanation

Case (a) Let `k_(1) = 40` N/m, `k_(2) = 30` N/m
the springs are connected in parallel
`therefore K = k_(1) + k_(2)`
` = 40 + 30 = 70` N/m
Elongation `y_(2) = (mg)/(K) = (2xx 9.8)/(90) = 0.21` m
`T = 2pisqrt((m)/(K)) = 2pi sqrt((2pi)/(90))`
` = 0.03` s