IB Physics SL A.3.11 Elastic Potential Energy

Practise calculating elastic energy from spring constant and extension, interpreting force-extension area and combining spring energy with gravitational or kinetic energy changes.

Exam points

calculate EH = ½k(Δx)² using extension from natural length rather than the spring's total length
obtain elastic energy as the area under a force-extension graph when the force is not simply constant
equate elastic energy with kinetic or gravitational energy to find speed, extension or spring constant

[Maximum number: 2]

An elastic climbing rope is tested by fixing one end of the rope to the top of a crane. The other end of the rope is connected to a block which is initially at position A. The block is released from rest. The mass of the rope is negligible.

Figure for Question A.3.11—Elastic potential energy question 1 — IB Physics SL

The unextended length of the rope is 60.0 m . From position A to position B, the block falls freely.

The length reached by the rope at C is 77.4 m . Suggest how energy considerations could be used to determine the elastic constant of the rope.

k can be determined using EPE $=\frac{1}{2} k x^{2}$

correct statement or equation showing

GPE at A=EPE at C

OR

( GPE+KE ) at B=EPE at C

Candidate must clearly indicate the energy associated with either position A or B for MP2.

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A.3.11—Elastic potential energy question 1