Physics College

A disk is rotating at 2 rev/sec. The disk has a moment of inertia of 25 kg m2. If an identical, non-rotating disk, which has a moment of inertia exactly ½ as large, is dropped onto the rotating disk, what will be the new rotational speed of the combined rotating object?

Answers

Answer 1

Answer: 8.38 revolutions per second

Explanation:

Before the second disk is dropped, the initial angular momentum of the system is given by:

L = I1 * w1

where I1 is the moment of inertia of the first disk, and w1 is its angular velocity.

Substituting the given values, we have:

L = (25 kg m^2) * (2 rev/sec * 2π rad/rev) = 100π kg m^2/s

When the second disk is dropped onto the rotating disk, the total moment of inertia of the system will be the sum of the moment of inertia of the first disk and the moment of inertia of the second disk:

Itotal = I1 + I2/2

where I2/2 is the moment of inertia of the second disk, which is half as large as that of the first disk.

Substituting the given values, we have:

Itotal = (25 kg m^2) + (12.5 kg m^2) = 37.5 kg m^2

Conservation of angular momentum requires that the initial angular momentum of the system be equal to its final angular momentum, so:

L = Itotal * wf

where wf is the final angular velocity of the combined disk.

Solving for wf, we get:

wf = L / Itotal = (100π kg m^2/s) / (37.5 kg m^2) ≈ 8.38 rev/sec

Therefore, the new rotational speed of the combined rotating object is approximately 8.38 revolutions per second.

Related Questions

Determine the linear velocity of blood in the aorta with a radis of 1.5 cm, if the duration of systole is 0.25 s, the stroke volume is 60 ml.

Answers

Answer:

The linear velocity of blood in the aorta can be calculated using the equation:

v = Q / A

where v is the linear velocity, Q is the volume flow rate, and A is the cross-sectional area of the vessel.

The volume flow rate Q can be calculated using the equation:

Q = SV / t

where SV is the stroke volume and t is the duration of systole.

The cross-sectional area of the aorta can be calculated using the equation:

A = πr^2

where r is the radius of the aorta.

Given that the radius of the aorta is 1.5 cm, the stroke volume is 60 ml, and the duration of systole is 0.25 s, we can calculate the volume flow rate Q:

Q = SV / t = 60 ml / 0.25 s = 240 ml/s

Converting the units of Q to cm^3/s:

Q = 240 ml/s × 1 cm^3/1 ml = 240 cm^3/s

We can then calculate the cross-sectional area of the aorta:

A = πr^2 = π × (1.5 cm)^2 = 7.07 cm^2

Finally, we can calculate the linear velocity of blood in the aorta:

v = Q / A = 240 cm^3/s / 7.07 cm^2 = 33.9 cm/s

Therefore, the linear velocity of blood in the aorta is 33.9 cm/s.

Estimat the number and wattage of lamps. which would be required to illuminate a workshop space 60x1.5 meteres by means of lamps mounted 5 metres above the working Plane The average illumination required is about 100 wt. coefficient of utilisation = 0.4 luminous efficiency 16 lumens per watt. Assume a space-height ratio of unity and a cundle Power depreciation of 20%​

Answers

The number and wattage of lamps required to illuminate the workshop would be approximately 8 lamps and 70 watts respectively.

Wattage calculation

To estimate the number and wattage of lamps required to illuminate a workshop space of 60x1.5 meters, we can follow these steps:

Calculate the area of the workshop:

Area = length x widthArea = 60m x 1.5mArea = 90 square meters

Determine the total lumens required:

Lumens = area x average illuminationLumens = 90 sq m x 100 luxLumens = 9000 lumens

Adjust for the coefficient of utilization and luminous efficiency:

Effective lumens = lumens / (coefficient of utilization x luminous efficiency)Effective lumens = 9000 / (0.4 x 16)Effective lumens = 1406.25 lumens

Adjust for space-height ratio and candle power depreciation:

Effective lumens per lamp = effective lumens x space-height ratio x (1 - depreciation)Effective lumens per lamp = 1406.25 x 1 x (1 - 0.2)Effective lumens per lamp = 1125 lumens

Determine the number of lamps required:

Number of lamps = total lumens required / effective lumens per lampNumber of lamps = 9000 / 1125Number of lamps = 8 lamps (rounded up)

Determine the wattage of each lamp:

Wattage per lamp = effective lumens per lamp / luminous efficiencyWattage per lamp = 1125 / 16Wattage per lamp = 70.3 watts (rounded up)

Therefore, approximately 8 lamps with a wattage of 70 watts each would be required to illuminate the workshop space.

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3. Large amplitude vibrations produced when the of receiver of the applied forced vibration matches the

Answers

An object's amplitude dramatically increases when the frequency of the applied forced vibrations matches the object's natural frequency. Resonance describes this behavior.

Theory A wave's amplitude directly relates to the quantity of energy it can carry. A wave with a high amplitude carries a lot of energy, whereas one with a low amplitude carries only a little. A wave's strength is determined by the typical energy that moves through a given area in a certain amount of time and in a particular direction.The sound wave's amplitude grows in proportion to its strength. We perceive louder noises to be of higher intensity. Comparative sound intensities are frequently expressed using decibels (dB)

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125cm³ of a gas was collected at 15 °C and 755 mm of mercury pressure. Calculate the volume of the gas that will be collected at standard temperature and pressure

Answers

Answer:

119,2 см³

Explanation:

по формуле Клопейрона (P1×V1):T1=(P2×V2):T2

если из этой формулы найти V2, ответ будет равен примерно на 119,2 см³

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