Question

Lesson : Periodic Motion

1. A device that is used for medical diagnosis oscillates at a frequency of 6.7 X 10⁶ Hz. How much time does each oscillation take? What is also its angular frequency?

2. Determine the displacement of an object that is undergoing SHM whose angular

frequency is 20°/ sec and its amplitude is 300mm at t = 1.5 sec.

3. Write down at least three (3) real life situations where periodic motion is applicable.

Answer 1

1. $\nu=1/T\to T=1/\nu=1/(6.7\cdot10^6)=1.49\cdot10^{-7}\ (s)$

$\omega =2\pi\nu=2\cdot3.14\cdot6.7\cdot10^6=42076000\ (rad/s)$

2. $20 \ °/s=0.35\ rad/s$

For SHM $s=A\sin\omega t$ . If $t=0$ then $s=0$ .

$0.3=A\sin0.35 t\to0.3=A\sin0.35\cdot1.5\to A=0.6\ (m)$

$s=0.6\sin0.35t$

$\Delta s=0.3\ (m)$

3. The rocking chair, the tuning fork, the swing, the pendulum in the clocks, car shock absorber, musical instruments, hearing, cradle, bungee jumping.