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Fynjy0 [20]
3 years ago
12

A ballet dancer spins with 2.4 rev/s with her arms outstretched,when the moment of inertia about axis of rotation is 1 .With her

arms folded,the moment of inertia about the same axis becomes 0.61 . calculate the new rate of spin.
Physics
1 answer:
kow [346]3 years ago
5 0

Correct question is;

A ballet dancer spins with 2.4 rev/s with her arms outstretched,when the moment of inertia about axis of rotation is I. With her arms folded,the moment of inertia about the same axis becomes 0.6I about the same axis. Calculate the new rate of spin.

Answer:

4 rev/s

Explanation:

We are given;

Initial Angular velocity; ω_i = 2.4 rev/s

Initial moment of inertia; I_i = I

Final moment of inertia; I_f = 0.6I

From conservation of angular momentum, we have;

I_i × ω_i = I_f × ω_f

Where ω_f is the new rate of spin.

Thus, let's make it the subject to get;

ω_f = (I_i × ω_i/I_f)

Plugging in relevant values, we have;

ω_f = (I × 2.4/0.6I)

I will cancel out to give;

ω_f = 2.4/0.6

ω_f = 4 rev/s

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6 0
3 years ago
What energy change is associated with the reaction to obtain one mole of H2 from one mole of water vapor? The balanced equation
Yakvenalex [24]

Answer:

ΔH = 249 kJ/mol

Explanation:

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2H₂O(g) → 2H₂(g) + O₂(g)    (1)

To calculate the energy change to obtain one mole of H₂(g) from one mole of H₂O(g), the coefficients of the reaction (1) must be halved:

H₂O(g) → H₂(g) + 1/2O₂(g)    (2)

The enthalpy of the reaction (2) is given by:

\Delta H = \Delta H_{r} - \Delta H_{p}  

<em>Where \Delta H_{r}: is the bond enthalpy of reactants and \Delta H_{p}: is the bond enthalpy of products.</em>

<u>For the reactants we have the next bond energies:</u>

2 x (H-O) = 2 x (467)

<u>And the bond energies for the products are:</u>

H-H + (1/2) (O=O) =  436 + (1/2)(498)

So, the enthalpy of the reaction (2) is:

\Delta H = 2 \cdot 467 kJ/mol - 436 kJ/mol - \frac{1}{2} \cdot 498 kJ/mol = 249 kJ/mol  

I hope it helps you!    

3 0
3 years ago
Identify each energy exchange as primarily heat or work and determine whether the sign of ΔE is positive or negative for the sys
geniusboy [140]

Answer:

(a)Work done and ΔE are negative

(b)Work done and ΔE are negative

(c)Work done and ΔE are positive

Explanation:

(a) When the two balls collide, the first billiard ball transfers its kinetic energy to the second ball which consequently starts rolling as the system ball comes to rest. Therefore, the decrease in internal energy takes places for both the system and energy transfer. Conclusively, Work done and ΔE are negative

(b) The drop of a book in this case system from a height transfers the potential energy to kinetic energy. Therefore, both the work is done by system on the floor and internal energy of the system decreases. In conclusion, Work done and ΔE are negative

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5 0
3 years ago
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