a, Wd=\(12\) J

b, x=±A/căn2

a, v=4cos(πt) (cm/s)

b, x=4/πcos(πt−2π​) (cm)

a=4πcos(πt+2π​) (cm/s²)

a, x=2,5 cm

v=-5căn30 cm/s

a=-100 cm/s2

b, x=2,5căn3 cm

v=-5pi cm/s

a=-căn3 cm/s2

a. Ở thời điểm \(t = 5\) s

\(x = 5 sin ⁡ \left(\right. 2 \pi . 5 + \frac{\pi}{6} \left.\right) = 2 , 5\) cm

\(\text{v} = 10 \pi cos ⁡ \left(\right. 2 \pi . 5 + \frac{\pi}{6} \left.\right) = 5 \sqrt{30}\) cm/s

\(a = - \omega^{2} x = - \left(\left(\right. 2 \pi \left.\right)\right)^{2} . 2 , 5 = - 100\) cm/s²

b. Khi pha dao động là 120^o.

\(x = 5 sin ⁡ 12 0^{o} = 2 , 5 \sqrt{3}\) cm

\(v = 10 \pi cos ⁡ 12 0^{o} = - 5 \pi\) cm/s

\(a = - \omega^{2} x = - 4 \pi^{2} . 2 , 5 \sqrt{3} = - \sqrt{3}\) cm/s

v=8√2 cm/s

a=8cm/\(s^2\)

8cos(\(\frac{\pi}{2}\)t + \(\frac{\pi}{2}\))