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A heavy solid disk rotating freely and slowed only by friction applied at its outer edge takes 120 seconds to come to a stop.

alisha [4.7K]

Answer:

The time is 16 min.

Explanation:

Given that,

Time = 120 sec

We need to calculate the moment of inertia

Using formula of moment of inertia

$I=\dfrac{1}{2}MR^2$

If the disk had twice the radius and twice the mass

The new moment of inertia

$I'=\dfrac{1}{2}\times2M\times(2R)^2$

$I'=8I$

We know,

The torque is

$\tau=F\times R$

We need to calculate the initial rotation acceleration

Using formula of acceleration

$\alpha=\dfrac{\tau}{I}$

Put the value in to the formula

$\alpha=\dfrac{F\times R}{\dfrac{1}{2}MR^2}$

$\alpha=\dfrac{2F}{MR}$

We need to calculate the new rotation acceleration

Using formula of acceleration

$\alpha'=\dfrac{\tau}{I'}$

Put the value in to the formula

$\alpha=\dfrac{F\times R}{8\times\dfrac{1}{2}MR^2}$

$\alpha=\dfrac{2F}{8MR}$

$\alpha=\dfrac{\alpha}{8}$

Rotation speed is same.

We need to calculate the time

Using formula angular velocity

$\Omega=\omega'$

$\alpha\time t=\alpha'\times t'$

Put the value into the formula

$\alpha\times120=\dfrac{\alpha}{8}\times t'$

$t'=960\ sec$

$t'=16\ min$

Hence, The time is 16 min.

5 0

3 years ago

Is the water the same temperature in alaska and mexico?

Snezhnost [94]

Colder in Alaska, warmer in Mexico.

6 0

3 years ago

Describe four consequences of having a different type of joint in the thumb.

Mariulka [41]

Answer:

Essentially, your thumb is the main piece of your body that has saddle joints. The bones in your seats joint are in charge of moving forward and backward, side to side.

When all is said in done, the piece of the thumb joint that is subjected to extreme anxiety is that known as CMC joint or carpometacarpal joint. This joint is fundamentally shaped by the metacarpal bone and it explains with the trapezium bone of the wrist.

Explanation:

5 0

2 years ago

A moose runs through the woods and covers 825 m North in 118 s. What is the average velocity of the moose?

weqwewe [10]

Total displacement=825m
Total Time=118s

Average Velocity=Total Displacement/Total Time

$\\ \sf\longmapsto Average\: Velocity=\dfrac{825}{118}$

$\\ \sf\longmapsto Average\:Velocity\approx 8m/s$

4 0

2 years ago

A rescue team is searching for Andrew, a geologist who was stranded while conducting research in the mountains of Colorado. The

Sindrei [870]

Answer:

I = 9.82 10⁻⁷ W / m²

Explanation:

The intensity of the sound wave is the energy of the wave between the order per unit area of the same

I = P / A = E / T A

the energy is calculated by integrating the mechanical energy in a period, where the mass is changed by the density and ‘s’ is the amplitude of the sound wave

I = ½ ρ v (w s)²

I = ½ 1.35 328 (2π 530 2.00 10⁻⁸)²

I = 221.4 (4.435 10⁻⁹)

I = 9.82 10⁻⁷ W / m²

4 0

3 years ago