← Mechanical Systems: past papers
AS 91524 · 2025 paper · simple harmonic motion
Question 3(a) Achieved
Practises Simple harmonic motion (SHM)
Rīhari swings a ball on a string as a pendulum. It is 1.20 m from the fixed point to the ball's centre of mass, and the ball is released 5.60° from the vertical. The string's mass is insignificant.
| L | 1.20 m |
|---|---|
| θ | 5.60° |
Show that the maximum displacement of the ball is 0.117 m.
Work it out
Try it on paper first. Stuck? Take one hint at a time.
-
1 Draw the string at 5.60° to the vertical. Which side of the triangle is the ball’s sideways displacement?
The 1.20 m string is the hypotenuse, and the sideways displacement is the side opposite the 5.60° angle. -
2 Which trig ratio links the opposite side to the hypotenuse?
sin θ = A / l, so A = 1.20 × sin 5.60° = 0.117 10 m.
What the marker wanted
- Achieved The right answer, worked with sine.
In our words, from NZQA’s 2025 marking schedule.
How did it go?
Got it moves it further out. Review brings it back tomorrow.