Answer:
90degrees I'm pretty sure
Depending on which type of motor you're talking about, but the first 3 are true. A stronger magnetic field in a DC motor will slow it down but increase its torque.
The amount of current in the motor will control the magnetic fields and therefore affect the speed (and torque). In an induction motor, the rotational speed is given by

where f is the line frequency and p is the number of poles. Thus fewer poles makes it go faster.
Answer:
2587.2 J.
Explanation:
From potential energy,
The work done to lift the chain = potential energy of the chain.
W = mgh............... Equation 1
Where W = work done to lift the chain, m = mass of the chain, g = acceleration due to gravity of the chain, h = height of the chain.
But,
m = m'd............... Equation 2
Where m' = density of the chain, d = length of the chain.
Substitute equation 2 into equation 1
W = m'dgh................ Equation 3
Given: m' = 2 kg/m, d = 12 m, h = 11 m, g = 9.8 m/s²
Substitute into equation 3
W = 2(12)(11)(9.8)
W = 2587.2 J.
Velocity=frequency/wavelength
frequency=velocity*<span>wavelength
</span>f=341*0.8
f=272.8 Hz