Physics, 08.12.2020 16:10 joexx6507

A person stands, hands at their side, on a platform that is rotating at a rate of 1.50 rev/sec. When they raise their hands to a horizontal position, the rate of rotation decreases to 0.70 rev/sec. By what factor has their moment of inertia changed going from hands at side to hands outstretched? a. 2.14
b. 1.05
c. 0.467
d. None

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Answer from: russianspartan1

The value is k = 2. 14

Explanation:

From the question we are told that

The angular speed of the platform when the hands are on the side is $w_1 = 1.50 \ rev / sec$

The angular speed of the platform when the hands are in horizontal position is

$w_2 = 0.70 \ rev / sec$

Generally the angular momentum of the system (the person and the platform) when the person's hand is at the side is

L_1 = I_1 * w_1

Generally the angular momentum of the system (the person and the platform) when the person's is stretched out horizontally is

L_2 = I_2 * w_2

Generally from the law of angular momentum conservation we have that

L_1 = L_2

=> I_1 * w_1 = I_2 * w_2

=> $I_2 = \frac{w_1}{w_2} * I_1$

=> $I_2 = \frac{1.50 }{0.70} * I_1$

=> I_2 = 2.14 I_1

So the factor by which moment of inertia changed is k = 2. 14

Answer from: Quest

19 hertz bruh u trippin? ?

Answer from: Quest

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

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A person stands, hands at their side, on a platform that is rotating at a rate of 1.50 rev/sec. When...

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