For a current-carrying wire running perpendicular to a magnetic field, the magnetic force acting on the wire is given by:
F = ILB
F = magnetic force, I = current, L = wire length, B = magnetic field strength
Given values:
F = 0.60N, L = 1.0m, B = 0.20T
Plug in and solve for I:
0.60 = I(1.0)(0.20)
I = 3.0A
Answer:
part (a) 
part (b) N = 79.61 rev
part (c) 
Explanation:
Given,
- Initial speed of the wheel =

- total time taken = t = 20.0 sec
part (a)
Let
be the angular acceleration of the wheel.
Wheel is finally at the rest. Hence the final angular speed of the wheel is 0.

part (b)
Let
be the total angular displacement of the wheel from initial position till the rest.

We know, 1 revolution =
rad
Let N be the number of revolution covered by the wheel.

Hence the 79.61 revolution is covered by the wheel in the 20 sec.
part (c)
Given,
- Mass of the pole = m = 4 kg
- Length of the pole = L = 2.5 m
- Angle of the pole with the horizontal axis =

Now the center of mass of the pole = 
Weight component of the pole perpendicular to the center of mass = 

The sun is in the middle of the milky way and the planets in our solar system rotate around it