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3 years ago

Which statement best describes a scientific law?

Physics

1 answer:

Ivenika [448]3 years ago

6 0

<span>D. A statement that explains an observation
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In what way is the structure of the Milky Way galaxy similar to the structure of the solar system?

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It is the solar system because the planets are in it

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A contact force is a force that is exerted by an object when it touches another object. Which of the following is an example of

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3 years ago

If The density of this stainless steel is7.85 g/cm3,specific heatis 0.5 J/g.K, melting pointis 1673K, heat of fusion s0.260J/kg.

kodGreya [7K]

Answer:

$\Delta H=687.4 J$

Explanation:

Hello!

In this case, for this melting process, we can identify two sub-processes in order to take the stainless steel from solid to liquid:

1. Heat up from 298.15 K to 1673 K.

2. Undergo the phase transition.

Both process have an associated enthalpy as shown below:

$\Delta H_1=1g*0.5\frac{J}{g*K} (1673K-298.15K)=687.4J$

$\Delta H_2=0.001kg*\frac{0.260J}{kg} =0.00026J$

Therefore, the required heat is:

$\Delta H=\Delta H_1+\Delta H_2\\\\\Delta H=687.4J+0.00026J\\\\\Delta H=687.4J$

Notice the problem is not providing neither the mass or volume, that is why we assumed the mass is 1 g; however, it can be changed to the mass you are given.

Best regards!

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3 years ago

How long will it take a 2.93 hp motor to lift a 250 kg beam directly upward at constant velocity from the ground to a height of

V125BC [204]

Answer: 50.4 s

Explanation:

The energy expended by the motor, must be equal to the work done by it, which is just equal to the change in the gravitational potential energy of the beam, as we are told that the beam is being lifted directly upward at constant speed (so, the applied force is equal and opposite at any time to the gravity force on the beam) , as follows:

W = m*g*h = 250 kg. * 9.8 m/s²* 45.0 m = 110,250 J

Now, as Power is just Energy / Time, we need just to solve for time this equation.

But, prior to be able to solve this equation, we need that our units be consistent.

As we are given the motor power in HP, we need to convert this unit to Joules/seg, as follows:

1 HP = 746 W

2.93 HP = 2.93 HP * (746W/1HP) = 2,186 J/s

Solving the Power equation for t:

t = W/P = 110,250 J / 2,186 J/s = 50.4 s

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