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3 years ago

How much thermal energy is needed to melt 1.25 kg of water at its melting point? Use Q = masslaten heat of fusion.

Physics

1 answer:

Amanda [17]3 years ago

8 0

Answer:

Latent heatnof fusion = 417.5 J

Explanation:

Specific latent heat of fusion of water is 334kJ.kg-1.

The heat required to melt water when it's ice I called latent heat because there is no temperature change, the only change observed is change in physical structure.

The amount of heat required to change 1 kg of solid to its liquid state (at its melting point) at atmospheric pressure is called Latent heat of Fusion.

Latent heat = ML

Latent heat= 1.25 kg * 334kJ.kg-1

Latent heat = 1.25*334 *(J/kg)*kg

Latent heat = 417.5 J

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A student measures the volume of a gas sample at several different temperatures. The results are tabulated as follows:Temperatur

lapo4ka [179]

Answer:

Check the first and the third choices:

a. The temperature of a gas is directly proportional to its volume

b. The temperature-to-volume ratio of a gas is constant.

Explanation:

Rewrite the table for better understanding:

Temperature of gas (K) Volume of gas (L)

298 4.55

315 4.81

325 4.96

335 ?

Calculate the ratios temperature to volume with 3 significant figures:

298 / 4.55 = 65.5

315 / 4.81 = 65.5

325 / 4.96 = 65.5

Then, those numbers show a constant temperature-to-volume ratio, which may be expressed in a formula as:

Temperature / Volume = constant, which is a directly proportional variation (the volume increases in a constant proportion to the increase of the temperature).

Hence, the correct choices are:

The temperature of a gas is directly proportional to its volume (first statement), and

The emperature-to-volume ratio of a gas is constant (third statement).

5 0

3 years ago

Which tuning forks will give rise to a beat frequency of 20 Hz when sounded together with a 240 Hz tuning fork?

Lubov Fominskaja [6]

Use the concept of beat frequency to find the applicable final freqeuncy for 20Hz beat frequency.

Beat can be defined as 'the interference pattern between two sounds of slightly different frequencies0

The expression for beat frequency is given as

$f_{beat} = |f_1-f_2|$

Where,

$f_2 =$ Final frequency

$f_1 =$ Initial frequency

The beat frequency for us is 25Hz and the initial frequency is 240Hz, then

$20= |f_2-240|$

Being an absolute value, two values are possible, both in addition and subtraction:

$f_2 = 240 \pm 20$

The two possible values are

$f_2 = 220Hz$

$f_2 = 260Hz$

3 0

3 years ago

A boulder of mass 2000. kg breaks loose of a mountainside and plunges 200. m straight down into a lake at a temperature of 5.00◦

natka813 [3]

Answer:

DS = 13865.7[J/K]

Explanation:

We can calculate the energy of the rock, like the potential energy relative to the lake level. Which can be calculated by means of the following expression of the potential energy:

$E_{p}=m*g*h\\\\where:\\m = mass = 2000[kg]\\h = elevation = 200 [m]\\g = gravity = 9.81[m/s^2]$

Therefore:

$E_{p}=2000*9.81*200\\E_{p}=3924000 [J]\\$

This energy is transformed into thermal energy.

we shall remember that isothermal heat transfer processes are internally reversible, so the entropy change of a system during one of these processes can be determined, by the following expression.

$DS=\frac{Q}{T}\\ where:\\DS = entropy change [J/K]\\Q = Heat transfer [J]\\T = temperature [K]$

T = 5 + 278 = 283[K]

DS = 3924000 / 283

DS = 13865.7[J/K]

5 0

3 years ago

You are performing a knee extension exercise. You hold a 20kg weight at full knee extension. The weight is 0.4m from your knee j

dmitriy555 [2]

Answer:

The moment is -78.4 N-m (clockwise).

Explanation:

Given:

Mass of the object (m) = 20 kg

Distance of the object from the knee joint (d) = 0.4 m

Weight of leg is not considered.

Acceleration due to gravity (g) = 9.8 m/s²

Now, weight of the object is equal to the product of its mass and acceleration due to gravity. So,

Weight = Mass × Acceleration due to gravity

= $mg=20\times 9.8 =196\ N$

We know that, moment of a force about a point is defined as the product of force applied and the perpendicular distance between the point and the line of application of force.

Moment of the given weight about the knee joint is given as:

Moment about knee joint = Weight × Distance from knee joint to weight

Moment about knee joint = 196 × 0.4 = 78.4 Nm

Now, from the diagram below, we can observe that, the weight acts vertically down and thus the sense of rotation about the knee joint at point O is clockwise. So, moment is negative.

Therefore, the moment is -78.4 N-m (clockwise).

7 0

3 years ago

In a lab, the mass of object A is 2.5 kg. Object A weighs:

dangina [55]

Answer:

25N

Explanation:

Assuming the lab is on earth:

w = mg = 2.5 (9.81) = 25N

8 0

3 years ago