<span>Density is a value for
mass, such as kg, divided by a value for volume, such as m3. Density is a
physical property of a substance that represents the mass of that substance per
unit volume. To find the mass of the substance, we need to multiply the volume occupied by the substance.
Mass = Density x Volume
Mass = 7.9 g/cm^3 (5.5 cm)^3
Mass = 43.45 g </span>
To solve this problem we need to use the proportional relationships between density, mass and volume, together with Newton's second law.
The force can be described as

Where,
m = Mass
g = Gravitational acceleration
At the same time the Density can be defined as

Where,
m = mass
V = Volume
Replacing the value of the mass at the equation of Force we have,

Since the difference between the two forces gives us the total Force then we have to

Where
Force of the water
= Force of plastic
Therefore with the values for this force we have,





Therefore the tension in the thread is 16.412N
INDUCTION MOTOR:-
Speed:-Less speed range than PMAC motors • Speed range is a function of the drive being used — to 1,000:1 with an encoder, 120:1 under field-oriented control
Reliability:-Waste heat is capable of degrading insulation essential to motor operation • Years of service common with proper operation
Power density:-Induction produced by squirrel cage rotor inherently limits power density
Accuracy:-Flux vector and field-oriented control allows for some of accuracy of servos
Cost:-Relatively modest initial cost; higher operating costs
PERMANENT MAGNET MORTOR:-
speed:-VFD-driven PMAC motors can be used in nearly all induction-motor and some servo applications • Typical servomotor application speed — to 10,000 rpm — is out of PMAC motor range
Reliability:-Lower operating temperatures reduces wear and tear, maintenance • Extends bearing and insulation life • Robust construction for years of trouble-free operation in harsh environments.
power density:-Rare-earth permanent magnets produce more flux (and resultant torque) for their physical size than induction types.
Accuracy:-Without feedback, can be difficult to locate and position to the pinpoint accuracy of servomotors
<span>Cost:-Exhibit higher efficiency, so their energy use is smaller and full return on their initial purchase cost is realized more quickly</span>