Can sonebody help answer and explain this problem:

the problem is in the picture.

Explanation:

"Rank the magnitude of the torque the signs exert about the point at which the rod is attached to the side of the building."

Torque is the cross product of the radius vector and force vector.

τ = r × F

The magnitude of the torque is the force times the perpendicular distance.  In other words, it is the force times distance times the sine of the angle between them.

τ = F r sin θ

Let's assume the length of each rod is L meters.  In each case, the weight is a vertical force, so the perpendicular distance is the horizontal distance between the wall and the sign.

A) τ = (50 kg × 10 m/s²) (L sin 30° m)

τ = 250L Nm

B) τ = (100 kg × 10 m/s²) (L m)

τ = 1000L Nm

C) τ = (50 kg × 10 m/s²) (L sin 60° m)

τ ≈ 433L Nm

D) τ = (90 kg × 10 m/s²) (L m)

τ = 900L Nm

Ranked from greatest to least:

B > D > C > A

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation: