Mass of the block = 1.4 kg
Weight of the block = mg = 1.4 × 9.8 = 13.72 N
Normal force from the surface (N) = 13.72 N
Acceleration = 1.25 m/s^2
Let the coefficient of kinetic friction be μ
Friction force = μN
F(net) = ma
μmg = ma
μg = a
μ = 
μ = 
μ = 0.1275
Hence, the coefficient of kinetic friction is: μ = 0.1275
Answer:

Explanation:
Given data
Speed v=2650 km/h
Radius r=85.0 km
To find
Centripetal Acceleration
Solution
As centripetal acceleration is given as

where
v is velocity
r is the radius
Substitute the given values in eq(i)

Fnet=F1+F2 or Fnet=F1-F2
So 400n up - 600n down
Fnet= 400-600= -200N
You look at the units you want, then try to figure out which units ti multiply by to get the units you have to match the units you want. For example, if you want kg/m^3 and have m/s
You can see that you have a length/time(lets denote it d/t for distance over time) and want mass/volume (lets denote it m/d^3). d/t multiplied by time=d but we want m/d^3 so lets multiply our original d/t by time(t) and mass(m) so d/t(t) (m) =dm. However, we want m/d^3 so we will also have to divide by d^4.
(d/t)(t)(m) /(d^4)=m/d^3 = mass/length^3 =mass/volume which was what we wanted our end result to be.
I think this would have to be equal because the wall is not moving away
from or into your hit so therefore your force is just as equal as the
walls force