Can you please stop pasting this question, just go to his profile and ask him.
Answer:

Explanation:
F = Force on the sled = 63 N
m = Mass of sled = 28.7 kg
= Coefficient of kinetic friction = 0.169
g = Acceleration due to gravity = 
The force balance of the system is given by

The acceleration of the sled is
.
Answer:

Explanation:
The force of kinetic friction on the block is defined as:

Where
is the coefficient of kinetic friction between the block and the surface and N is the normal force, which is always perpendicular to the surface that the object contacts. So, according to the free body diagram of the block, we have:

Replacing this in the first equation and solving for
:

Answer:

Explanation:
As we know that the sixth order maximum will have path difference given as

here we know that
N = order of maximum

now we have

so we know that


Electrostatic attraction. The stronger the electric field, the greater the electrostatic force.