Question

When a 1.0kg mass hangs attached to a spring of length 50 cm, the spring stretches by 2 cm. The mass is pulled down until the length of the spring becomes 60 cm. What is the amount of elastic energy stored in the spring in this condition, if g = 10 m/s²

• A. 1.5 Joule
• B. 2.0 Joule
• C. 2.5 Joule
• D. 3.0 Joule

Answer 1

Answer: (C)

2.5 Joule

Answer 2

Force constant of a spring

$k = \frac { F } { x } = \frac { m g } { x } = \frac { 1 \times 10 } { 2 \times 10 ^ { - 2 } }$ ⇒ $k = 500 \mathrm {~N} / \mathrm { m }$

Increment in the length = 60 – 50 = 10 cm