A `50 g` mass hangs at the end of a massless spring. When `20 g` more are added to the end of the spring, it stretches `7.0 cm` more. (a) Find the spring constant. (b) If the `20 g` are now removed, what will be the period of the motion ?

Answer

A, B, D

Explanation

(a) `kx = mg`
`:. k = (mg)/(x) = ((20 xx 10^(-3))(10))/(7xx10^(-2))`
`= (20)/(7)N//m`
(b) `T = 2pi sqrt ((m)/(k))`
`= 2pi sqrt ((50 xx10^(-3))/(20//7))` = 0.84 s`