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.
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Answer:
Magnitude of the force is 2601.9 N
Explanation:
m = 450 kg
coefficient of static friction μs = 0.73
coefficient of kinetic friction is μk = 0.59
The force required to start crate moving is
.
but once crate starts moving the force of friction is reduced
.
Hence to keep crate moving at constant velocity we have to reduce the force pushing crate ie
.
Then the above pushing force will equal the frictional force due to kinetic friction and constant velocity is possible as forces are balanced.
Magnitude of the force

Explanation:
A metal such as copper is a <u>conductor</u> because it provides a pathway for electric charges to move easily. A material such as rubber is an <u>insulator</u> because it <u>resists</u> the flow of electric charges. A material that partially conducts electric current is a <u>semiconductor</u>. These materials include <u>group 3 and group 5</u> elements.
Answer:
it is True as the operational definition of electric current.
Explanation:
The definition of electric current is
I = dQ / dt
By convention the direction of the current is the direction in which a positive charge flows.
The initial expression is the derivative that is the change of the load in the unit of time and this occurs in a given cross-sectional cable.
The proposed definition is the same as this, so it is True as the operational definition of electric current.
Answer:
Speed, mass and acceleration
Explanation:
A scalar quantity is a quantity that has only magnitude but no direction while a vector quantity has both magnitude and direction.
According to the question, the row that has two scalars and one vector is speed, mass and acceleration.
The two scalars in this row are speed and mass while the vector quantity there is the acceleration.
Acceleration has direction since it possess direction. A body accelerating will do so in a particular direction. Speed and mass doesn't possess any direction. Mass only specify the magnitude of the body but no clue as to which direction is the body moving towards.
Speed also only specify the
total distance covered with respect to time but not the direction of the direction.