Answer:
The angular speed of the new system is
.
Explanation:
Due to the absence of external forces between both disks, the Principle of Angular Momentum Conservation is observed. Since axes of rotation of each disk coincide with each other, the principle can be simplified into its scalar form. The magnitude of the Angular Momentum is equal to the product of the moment of inertial and angular speed. When both disks begin to rotate, moment of inertia is doubled and angular speed halved. That is:

Where:
- Moment of inertia of a disk, measured in kilogram-square meter.
- Initial angular speed, measured in radians per second.
- Final angular speed, measured in radians per second.
This relationship is simplified and final angular speed can be determined in terms of initial angular speed:

Given that
, the angular speed of the new system is:


The angular speed of the new system is
.
A) lithium and beryllium
Explanation:
From the given row on the periodic table, only lithium and beryllium will conduct electricity.
What makes a substance able to conduct electricity?
- The presence of free mobile electrons and in some, ions allows them to carry electric currents.
Metals are generally known to be good conductors of heat and electricity. This is because, metals have a large pool of electrons i.e free mobile electrons. They are electropositive with a large size and readily release their electrons for conduction.
Lithium and Beryllium are in the metallic block on the periodic table.
Learn more:
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Answer:
q=1.4*10^{-9}C
Explanation:
Given data:
charge on ruler = -14μC
Mass of tissue is 5 g
To Know the minimum charge, equate electrostatic force to weight
we have F = W
so
putting all value in equation,

solving for q

or q=1.4*10^{-9}C