Answer:

Explanation:
We are given that
Diameter of wire=d=4.12 mm
Radius of wire=r

Current=I=8 A
Drift velocity=
We have to find the density of free electrons in the metal
We know that
Density of electron=
Using the formula
Density of free electrons=
By using Area of wire=

Density of free electrons=
In order to find the solid, you would want the object in which sound travels the fastest
In this case, since in object C, the speed of sound is the fastest, it is the most likely to be a solid
So object C is most likely to be a solid
Answer:
3. µs g /7
Explanation:
The largest Force appear when the maximal friction Force is required.
Second Newton law for the small block:



Second Newton law for the Big Block:



Answer:
The distance travel by block before coming to rest is 0.122 m
Explanation:
Given:
Mass of block
kg
Initial speed of block

Final speed of block

Coefficient of kinetic friction 
Ramp inclined at angle
28.4°
Using conservation of energy,
Work done by frictional force is equal to change in energy,

Where 



m
Therefore, the distance travel by block before coming to rest is 0.122 m
Answer:
The electric force on the top charge is
.
Explanation:
Given that,
Electric charges in a thundercloud, 
The distance between charges, d = 2.3 km = 2300 m
Let F is the electric force on the top charge. The electric force is given by the formula as :



or

So, the electric force on the top charge is
. Hence, this is the required solution.