A particle is undergoing simple harmonic motion with period \( \frac{\pi}{3} \) - HSC - SSCE Mathematics Extension 2 - Question 13 - 2020 - Paper 1
Question 13
A particle is undergoing simple harmonic motion with period \( \frac{\pi}{3} \). The central point of motion of the particle is at \( x = -\sqrt{3} \). When \( t = 0... show full transcript
Worked Solution & Example Answer:A particle is undergoing simple harmonic motion with period \( \frac{\pi}{3} \) - HSC - SSCE Mathematics Extension 2 - Question 13 - 2020 - Paper 1
Step 1
Find an equation for the displacement, x, of the particle in terms of t.
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Answer
The equation has the form:
x(t)=Acos(nt)+C
Where:
(A = \frac{2}{\sqrt{3}})
(C = -\sqrt{3})
The angular frequency (n) is given by (n = \frac{2\pi}{T} = \frac{2\pi}{\frac{\pi}{3}} = 6)
Thus, substituting these values into the equation:
x(t)=32cos(6t)−3
Step 2
Consider the two lines in three dimensions given by ...
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Answer
To find the point of intersection, equate the components of the two lines:
Solving gives:
( -1 - 4 = 2h_1 - h_1 \Rightarrow h_1 = -5 ) and substituting back into equation gives (h_2 = -4.
Finally, substituting (h_1) and (h_2) back into the line equation gives the point of intersection as:
r=(−223−5)
Step 3
By considering the right-angled triangle below, or otherwise, prove that a + b \over 2 \geq \sqrt{ab}.
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Answer
By Pythagoras, we have:
(a+b)2=x2+(a−b)2⇒x2=(a+b)2−(a−b)2
The properties of the triangle imply:
(x \leq a + b)
Thus, it can be shown that:
( \frac{a + b}{2} \geq \sqrt{ab} ) using the inequality of means (AM-GM).
Step 4
Prove that p^2 + 4q^2 \geq 4pq.
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Answer
Let (p = a) and (q = b), then:
By following the derivation steps, we arrive at:
p2+4q2−4pq=(p−2q)2≥0,
which confirms that the inequality holds.
Step 5
Show that for any integer n, e^{iθ} + e^{-iθ} = 2cos(nθ).
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Answer
Using Euler's formula, we have:
eiθ=cos(θ)+isin(θ) and e−iθ=cos(θ)−isin(θ).
Thus,
eiθ+e−iθ=2cos(θ).
Step 6
By expanding (e^{iθ} + e^{-iθ})^2, show that cos^2(θ) = 1/8 (cos(4θ) + 4cos(2θ) + 3).
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Answer
Starting with:
(eiθ+e−iθ)2=2cos(θ)⋅2cos(θ)=4cos2(θ),
and using the cosine of double angle:
cos(2θ)=2cos2(θ)−1
we derive the required expression through expansions.
Step 7
Consequently, or otherwise, find \int_{0}^{\frac{\pi}{2}} \cos^2(θ) \, dθ.
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Using the identity derived:
∫02πcos2(θ)dθ=∫02π81(cos(4θ)+4cos(2θ)+3)dθ
Calculating each integral gives:
=[163π]−0+163π.
Finally, the answer results in ( \frac{3\pi}{16} ).