A mass is suspended vertically from a fixed point by means of a spring, as illustrated in Fig. 4.1. [Figure 4.1] The mass is oscillating vertically. The variation with displacement x of the acceleration a of the mass is shown in Fig. 4.2. [Figure 4.2]
- (a)(i)State what is meant by the displacement of the mass on the spring.[1]
- (a)(ii)Suggest how Fig. 4.2 shows that the mass is not performing simple harmonic motion.[1]
- (b)(i)The amplitude of oscillation of the mass may be changed. State the maximum amplitude x₀ for which the oscillations are simple harmonic.[1]
- (b)(ii)For the simple harmonic oscillations of the mass, use Fig. 4.2 to determine the frequency of the oscillations.[3]
- (c)The maximum speed of the mass when oscillating with simple harmonic motion of amplitude x₀ is v₀. On Fig. 4.3, show the variation with displacement x of the velocity v of the mass for displacements from +x₀ to –x₀. [Figure 4.3][2]
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Mark scheme
Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.
- [B1] (a)(i) distance from a (reference) point in a given direction
- [B1] (a)(ii) line is not straight or gradient is not constant
- [A1] (b)(i) 0.85–0.90 cm
- [C1] (b)(ii) a = − (2πf)² x
- [C1] (b)(ii) e.g. 1.2 = 4π² × f² × (0.90 × 10⁻²)
- [A1] (b)(ii) f= 1.8 Hz
- [B1] (c) complete circle/ellipse enclosing the origin
- [B1] (c) closed shape passing through (0,±v₀) and (±x₀, 0)
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