It is salt water because they are two things combined together.
Answer:

Explanation:
When top block is just or about to slide on the lower block then we can say that the frictional force on it will be maximum static friction
So we will have






now for the Net force on two blocks to move together



Answer:
μk = 0.26885
Explanation:
Conceptual analysis
We apply Newton's second law:
∑Fx = m*a (Formula 1)
∑F : algebraic sum of the forces in Newton (N)
m : mass in kilograms (kg)
a : acceleration in meters over second square (m/s²)
Data:
a= -0.9 m/s²,
g = 9.81 m/s² : acceleration due to gravity
W= 75 N : Block weight
W= m*g
m = W/g = 75/9.8= 7.65 kg : Block mass
Friction force : Ff
Ff= μk*N
μk: coefficient of kinetic friction
N : Normal force (N)
Problem development
We apply the formula (1)
∑Fy = m*ay , ay=0
N-W-25 = 0
N = 75
+25
N= 100N
∑Fx = m*ax
20-Ff= m*ax
20-μk*100
= 7.65*(-0.90 )
20+7.65*(0.90) = μk*100
μk = ( 20+7.65*(0.90)) / (100)
μk = 0.26885
Answer:

Explanation:
The torque exerted is given by

where
is the force applied
d = 3.10 cm = 0.031 m is the length of the lever arm
Substituting,

The equivalent of Newton's second law for rotational motion is:

where
is the net torque
I is the moment of inertia
is the angular acceleration
Solving the equation for I, we find
