Answer:
Two identical closely spaced circular disks form a parallel-plate capacitor. Transferring 2.1×109 electrons from one disk to the other causes the electric field strength between them to be 1.6×105 N/C. What are the diameters of the disks?
Explanation:
Check attachment for solution
Answer:
22J
Explanation:
Given :
radius 'r'= 3cm
rotational inertia 'I'=4.5 x
kgm²
mass on one side of rope '
'= 2kg
mass on other side of rope'
' =4kg
velocity'v' of mass
' = 2m/s
Angular velocity of the pulley is given by
ω = v /r => 2/ 3x 
ω = 66.67 rad/s
For the rotating body, we have
KE =
I ω²

= 10J
Next is to calculate kinetic energy of the blocks :

=12J
Therefore, the total kinetic energy will be
KE =
=10 + 12
KE= 22J
The given question is incomplete. The complete question is as follows.
A box of oranges which weighs 83 N is being pushed across a horizontal floor. As it moves, it is slowing at a constant rate of 0.90 m/s each second. The push force has a horizontal component of 20 N and a vertical component of 25 N downward. Calculate the coefficient of kinetic friction between the box and the floor.
Explanation:
The given data is as follows.
= 20 N,
= 25 N, a = -0.9
W = 83 N
m = 
= 8.46
Now, we will balance the forces along the y-component as follows.
N = W +
= 83 + 25 = 108 N
Now, balancing the forces along the x component as follows.
= ma
= 7.614 N
Also, we know that relation between force and coefficient of friction is as follows.

= 
= 0.0705
Thus, we can conclude that the coefficient of kinetic friction between the box and the floor is 0.0705.
Answer:
No
Explanation:
The force of tension exerted by the string on the rock acts as centripetal force, so its direction is always towards the centre of the circle.
However, the direction of motion of the rock is always tangential to the circle: this means that the force is always perpendicular to the direction of motion of the rock.
As we know, the work done by a force on an object is

where
F is the magnitude of the force
d is the displacement of the object
is the angle between the force and the displacement
In this situation, F and d are perpendicular, so
, therefore
and the work done is zero:
