The Moons of Mars,Phobos (Fear)and Deimos (Terror),are Very Close to the Planet

question 16

Multiple Choice

The moons of Mars,Phobos (Fear) and Deimos (Terror) ,are very close to the planet compared to Earth's Moon.Their orbital radii are 9,378 km and 23,459 km respectively.What is the ratio of the period of revolution of Phobos to that of Deimos?

• A) 0.2528
• B) 0.3998
• C) 1.582
• D) 2.858
• E) 3.956

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Definitions:

Pilot Devices

Control instruments that command the operation of electrical machinery indirectly, often through the use of relays or contactors.

Motor Starter

A device that controls the use of electrical power to equipment, especially to start and stop motors.

Control Coil

A coil used in a relay or other electrical device, which creates a magnetic field when electricity is passed through it, thereby controlling the operation of the device.

Two-wire Control

A control circuit configuration where only two conductors are used to complete the circuit between the control device and the equipment being controlled.