Question

When a 20 g mass hangs attached to one end of
a light spring of length 10cm, the spring
stretches by 2 cm. The mass is pulled down
until the total length of the spring is 14 cm. The
elastic energy, in Joule stored in the spring is-
(1) 4 x 10-2(2) 4 x 103
(3) 8 x 102
(4) 8 x 10-3​

Answer 1

Answer:

(2) 4×10³

Explanation:

Mass=20g= .02kg

L1= 10cm

L2=14cm

Increment in length= 14-10= 4cm= .04m

Spring constanr K= F/x                  F=mg  

assume g=10m/s⁻²

K= mg/x= .02×10÷.04= 5 N/m

elastic energy U= 1/2 Kx²= 1/2×5×(.04)²= .004 J= 4×10³ J

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