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2 years ago

Which statement best compares and contrasts two physical properties of matter?

Physics

1 answer:

Stolb23 [73]2 years ago

5 0

Answer:

Explanation:

Boiling points and melting points are similar because they both involve the change in a state of a material, but they are different because boiling point involves a change from a liquid to a gas and melting point involves a change from a solid to a liquid.

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How much energy must be transferred out of the system as heat q to lower its temperature to 0∘c? express your answer numerically

serg [7]

Answer:

Incomplete question:

Refer to the temperature versus time graph when answering the questions in Parts C through F. A system consists of 250 of water. The system, originally at = 21.0 , is placed in a freezer, where energy is removed from it in the form of heat at a constant rate. The figure shows how the temperature of the system takes to drop to, after which the water freezes. Once the freezing is complete, the temperature of the resulting ice continues to drop, reaching temperature after an hour. The following specific heat and latent heat values for water may be helpful.

specific heat of ice (at ) = 2.10 J/g K

latent heat of fusion (ice to water phase change at ) = 333.7 J/g

specific heat of water (at ) = 4.186 J/g K

latent heat of vaporization (water to steam phase change at ) = 2256 J/g

specific heat of steam (at ) = 2.01 J/g K

Answers:

Qtotal = 237775 J

Explanation:

To solve this exercise it is necessary to know that if the system is a single phase in which there is a temperature change or if it is a phase change at a single temperature. In the first case, the following formula would be used to calculate the amount of heat:

Q₁ = mCpΔT

Here

m is the mass = 250 g

Cp is the specific heat of ice = 2.1 J/g K

ΔT = 21 - 0 = 21°C = 294 K

In this case the amount of energy is

Q₁ = 250*2.1*294 = 154350 J

In the second case, where there is a phase change at a single temperature, the amount of heat is:

Q₂ = mLf

Here

Lf = latent heat of fusion (ice to water phase change) = 333.7 J/g

Substituting:

Q₂ = 250*333.7 = 83425 J

The total heat is:

Qtotal = 154350+83425=237775 J

7 0

2 years ago

A girl is sledding down a slope that is inclined at 30º with respect to the horizontal. The wind is aiding the motion by providi

OleMash [197]

Answer:

The sled required 9.96 s to travel down the slope.

Explanation:

Please, see the figure for a description of the problem. In red are the x and y-components of the gravity force (Fg). Since the y-component of Fg (Fgy) is of equal magnitude as Fn but in the opposite direction, both forces get canceled.

Then, the forces that cause the acceleration of the sled are the force of the wind (Fw), the friction force (Ff) and the x-component of the gravity force (Fgx).

The sum of all these forces make the sled move. Finding the resulting force will allow us to find the acceleration of the sled and, with it, we can find the time the sled travel.

The magnitude of the friction force is calculated as follows:

Ff = μ · Fn

where :

μ = coefficient of kinetic friction

Fn = normal force

The normal force has the same magnitude as the y-component of the gravity force:

Fgy = Fg · cos 30º = m · g · cos 30º

Where

m = mass

g = acceleration due to gravity

Then:

Fgy = m · g · cos 30º = 87.7 kg · 9.8 m/s² · cos 30º

Fgy = 744 N

Then, the magnitude of Fn is also 744 N and the friction force will be:

Ff = μ · Fn = 0.151 · 744 N = 112 N

The x-component of Fg, Fgx, is calculated as follows:

Fgx = Fg · sin 30º = m·g · sin 30º = 87.7 kg · 9.8 m/s² · sin 30º = 430 N

The resulting force, Fr, will be the sum of all these forces:

Fw + Fgx - Ff = Fr

(Notice that forces are vectors and the direction of the friction force is opposite to the other forces, then, it has to be of opposite sign).

Fr = 161 N + 430 N - 112 N = 479 N

With this resulting force, we can calculate the acceleration of the sled:

F = m·a

where:

F = force

m = mass of the object

a = acceleration

Then:

F/m = a

a = 479N/87.7 kg = 5.46 m/s²

The equation for the position of an accelerated object moving in a straight line is as follows:

x = x0 + v0 · t + 1/2 · a · t²

where:

x = position at time t

x0 = initial position

v0 = initial velocity

t = time

a = acceleration

Since the sled starts from rest and the origin of the reference system is located where the sled starts sliding, x0 and v0 = 0.

x = 1/2· a ·t²

Let´s find the time at which the position of the sled is 271 m:

271 m = 1/2 · 5.46 m/s² · t²

2 · 271 m / 5.46 m/s² = t²

The sled required almost 10 s to travel down the slope.

8 0

2 years ago

Passing an electric current through a certain substance produces oxygen and sulfur. This substance cannot be a(n)

Nezavi [6.7K]

Answer:

An Element

Explanation:

Such substance cannot be an element because an element cannot be chemically disintegrated (i.e it cannot be disintegrated via chemical reaction).

4 0

2 years ago

The boom hoisting sheave must have pitch diameters of no less than _______times the nominal diameter of the rope used.

alexira [117]

Answer:

18 times

Explanation:

According to the security purposes which is set under the rules and regulation OSHA, which describes all the rights to the worker.

In the boom hoist receiving system all the sheaves which are used should have a pitch diameter of rope not less than 18 times the diameter of the nominal rope which is used.

7 0

2 years ago

You are learning about energy transformations in science class. Mel and Sam's built this set-up to see if light energy could be

Allisa [31]

I think it might be heat energy. light transforms into heat energy

5 0

2 years ago