Answer:
I believe it's the bottom left :)
Explanation:
(A) 
The energy stored by the system is given by

where
P is the power provided
t is the time elapsed
In this case, we have
P = 60 kW = 60,000 W is the power
t = 7 is the time
Therefore, the energy stored by the system is

(B) 4830 rad/s
The rotational energy of the wheel is given by
(1)
where
is the moment of inertia
is the angular velocity
The moment of inertia of the wheel is

where M is the mass and R the radius of the wheel.
We also know that the energy provided is

So we can rearrange eq.(1) to find the angular velocity:

(C) 
The centripetal acceleration of a point on the edge is given by

where
is the angular velocity
R = 0.12 m is the radius of the wheel
Substituting, we find

Answer:
Electric field magnitude
E = K/qd
Where
K = kinetic energy of electron
d = electron distance
q = charge
Explanation:
Given the relationship between workdone and energy
Work-energy theorem:
Net workdone = Energy change
W = ∆E
In this case
W = ∆K.E
And,
∆K.E = K(final) - K(initial)
To stop the kinetic energy | K(final) = 0
K(initial) = K (given)
∆K.E = 0 - K = -K
Let the electric force on the electron has magnitude F.
And
W = -Fd = ∆K.E = -K
-Fd = -K
F = K/d .....1
The magnitude of the electric field E that can stop these electron in a distance d:
E = F/q ......2
Where q is the charge on electron.
substituting equation 1 to 2
E = (K/d)/q = K/qd
E = K/qd
Answer:
So speed of electron will be 
Explanation:
We have given potential difference V = 9.9 KV
Charge on electron 
So energy of electron 
This energy of electron will be equal to kinetic energy of electron
So 


So speed of electron will be 