Answer:
a)15 N
b)12.6 N
Explanation:
Given that
Weight of block (wt)= 21 N
μs = 0.80 and μk = 0.60
We know that
Maximum value of static friction given as
Frs = μs m g = μs .wt
by putting the values
Frs= 0.8 x 21 = 16.8 N
Value of kinetic friction
Frk= μk m g = μk .wt
By putting the values
Frk= 0.6 x 21 = 12.6 N
a)
When T = 15 N
Static friction Frs= 16.8 N
Here the value of static friction is more than tension T .It means that block will not move and the value of friction force will be equal to the tension force.
Friction force = 15 N
b)
When T= 35 N
Here value of tension force is more than maximum value of static friction that is why block will move .We know that when body is in motion then kinetic friction will act on the body.so the value of friction force in this case will be 12.6 N
Friction force = 12.6 N
Yes, they seem right to me.
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Answer:

Explanation:
From the question we are told that:
Potential difference 
New Capacitor 
Generally the equation for Capacitor capacitance is mathematically given by

Generally the equation for New p.d' is mathematically given by




The concept of momentum tells us that it is equivalent to the product between the mass and the velocity of the object, that is to say that in general it can be written as

Where,
m = mass
v = Velocity
Our values are given as,


Replacing we have that,


Therefore the magniude of the momentum of the pitched baseball is 