A turntable that turns 9 revolutions each second is located on top of a mountain

Question

A turntable that turns 9 revolutions each second is located on top of a mountain. Mounted on the turntable is a laser that emits a bright beam of light. As the turntable and laser rotate, the beam also rotates and sweeps across the sky. On a dark night, the beam reaches some clouds 10 km away. (a) How fast does the spot of laser light sweep across the clouds? (b) How fast does the spot of laser light sweep across clouds that are 20 km away? (c) At what distance will the laser beam sweep across the sky at the speed of light (the speed of light is 300000 km/s)? (We will learn that no material can travel at the speed of light; here we have a nonmaterial spot. Not only can it travel at the speed of light, at greater radial distances the nonmaterial spot can travel faster than the speed of light!)

Explanation / Answer

V=R*W ,,,,W=9*2*pi rad/s=18pi rad/s......V=18pi*R (R= radius where cloud is there)... a ) clouds are at 10Km distance so V=565.486km/s b ) clouds are at 20Km distance so V=1130.973km/s c ) if speed of beam is300000km/s then r=? ,,now 300000=18pi*R so R=5305.1647Km.When clouds are at a distance 5305.1647 we can expect the beam to travel with speed of light.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.