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soldi70 [24.7K]
3 years ago
14

A man stands on a platform that is rotating (without friction) with an angular speed of 2.4 rev/s; his arms are outstretched and

he holds a brick in each hand. The rotational inertia of the system consisting of the man, bricks, and platform about the central vertical axis of the platform is 6.2 kg · m2. By moving the bricks the man decreases the rotational inertia of the system to 2.0 kg · m2. (a) What is the resulting angular speed of the platform? rev/s
Physics
1 answer:
andrey2020 [161]3 years ago
4 0

Answer:

The resulting angular speed of the platform is 7.44 rev/s.

Explanation:

Given that,

Speed = 2.4 rev/s

Moment of inertia consist of the man  = 6.2 kg-m²

Moment of inertia by the bricks= 2.0 kg-m²

We need to calculate the resulting angular speed of the platform

Using law of conservation of momentum

L_{1}=L_{2}

I\omega_{1}=I\omega_{2}

\omega_{2}=\dfrac{I_{1}\omega_{1}}{I_{2}}

Where,

I_{1} = moment of inertia consist of  the man

I_{2} = moment of inertia by the bricks

\omega_{2} = angular speed of platform

Put the value into the formula

\omega_{2}=\dfrac{6.2\times2.4\times2\pi}{2.0}

\omega_{2}=46.74\ rad/s

\omega_{2}=\dfrac{46.74}{2\pi}\ rev/s

\omega_{2}=7.44\ rev/s

Hence, The resulting angular speed of the platform is 7.44 rev/s.

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Answer:

(a): F_e = 8.202\times 10^{-8}\ \rm N.

(b): F_g = 3.6125\times 10^{-47}\ \rm N.

(c): \dfrac{F_e}{F_g}=2.27\times 10^{39}.

Explanation:

Given that an electron revolves around the hydrogen atom in a circular orbit of radius r = 0.053 nm = 0.053\times 10^{-9} m.

Part (a):

According to Coulomb's law, the magnitude of the electrostatic force of interaction between two charged particles of charges q_1 and q_2 respectively is given by

F_e = \dfrac{k|q_1||q_2|}{r^2}

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For the given system,

The Hydrogen atom consists of a single proton, therefore, the charge on the Hydrogen atom, q_1 = +1.6\times 10^{-19}\ C.

The charge on the electron, q_2 = -1.6\times 10^{-19}\ C.

These two are separated by the distance, r = 0.053\times 10^{-9}\ m.

Thus, the magnitude of the electrostatic force of attraction between the electron and the proton is given by

F_e = \dfrac{(9\times 10^9)\times |+1.6\times 10^{-19}|\times |-1.6\times 10^{-19}|}{(0.053\times 10^{-9})^2}=8.202\times 10^{-8}\ \rm N.

Part (b):

The gravitational force of attraction between two objects of masses m_1 and m_1 respectively is given by

F_g = \dfrac{Gm_1m_2}{r^2}.

where,

  • G = Universal Gravitational constant = 6.67\times 10^{-11}\ \rm Nm^2/kg^2.
  • r = distance of separation between the masses.

For the given system,

The mass of proton, m_1 = 1.67\times 10^{-27}\ kg.

The mass of the electron, m_2 = 9.11\times 10^{-31}\ kg.

Distance between the two, r = 0.053\times 10^{-9}\ m.

Thus, the magnitude of the gravitational force of attraction between the electron and the proton is given by

F_g = \dfrac{(6.67\times 10^{-11})\times (1.67\times 10^{-27})\times (9.11\times 10^{-31})}{(0.053\times 10^{-9})^2}=3.6125\times 10^{-47}\ \rm N.

The ratio \dfrac{F_e}{F_g}:

\dfrac{F_e}{F_g}=\dfrac{8.202\times 10^{-8}}{3.6125\times 10^{-47}}=2.27\times 10^{39}.

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