Answer:

Explanation:
Ok, the average speed can be calculate with the next equation:
(1)
Basically the car cover the same distance "d" two times, but at different speeds, so:

and the total time would be the time t1 required to go from A to B plus the time t2 required to go back from B to A:

From basic physics we know:

so:


Using the previous information in equation (1)

Factoring:
(2)
Finally, replacing the data in (2)

Answer: 2.80 N/C
Explanation: In order to calculate the electric firld inside the solid cylinder
non conductor we have to use the Gaussian law,
∫E.ds=Q inside/ε0
E*2πrL=ρ Volume of the Gaussian surface/ε0
E*2πrL= a*r^2 π* r^2* L/ε0
E=a*r^3/(2*ε0)
E=6.2 * (0.002)^3/ (2*8.85*10^-12)= 2.80 N/C
They have the same velocity because their displacements (shortest line from point A to point B, which is a straight line) are the same and they meet at the same time.
Answer:

Upward
Explanation:
We are given that
Mass of scarp paper,
1mg=
Distance,d =8 mm=
Magnitude of electric force =
Where 
Substitute the values


Gravitational force act in downward direction.
The electric force acts in opposite direction and magnitude of electric force is equal to gravitational force.
Hence, the direction of electric force is upward.
B. five electrons
If you want an explanation, here it is.
The atomic number gives the number of protons. Protons which have a positive charge are balanced by an equal number of electrons in a neutral atom. Boron number 5 has five protons and therefore as a neutral atom also has five electrons.