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s344n2d4d5 [400]
3 years ago
5

Five metal samples, with equal masses, are heated to 200oC. Each solid is dropped into a beaker containing 200 ml 15oC water. Wh

ich metal will cool the fastest? A) aluminum B) copper C) gold D) platinu Which sample of copper would demonstrate the GREATEST increase in temperature if 500 J of energy were added to the sample? A) 0.5 kg B) 1.0 kg C) 1.5 kg D) 2.0 kg Eliminate
Physics
1 answer:
Ksju [112]3 years ago
4 0
Part 1) Which metal will cool the fastest?
To answer this question, we should have a look at the formula of the heat flow rate, which says "how fast" a material is able to heat/cool:
\frac{\Delta Q}{\Delta t}  = -k  \frac{A \Delta T}{x}
where:
\Delta Q is the heat exchanged
\Delta t is the time interval
k is thermal conductivity of the material
A the  surface where the exchange of heat occurs
\Delta T the variation of temperature
x is the thickness of the material
We see that the heat flow rate \frac{\Delta Q}{\Delta t} is linearly proportional to k, the thermal conductivity of the material. So, the larger k, the fastest the metal will cool. 
If we have a look at the thermal conductivity of each metal, we find:
- Aluminium: 237 W/(mK)
- Copper: 401 W/(mK)
- Gold: 314 W/(mK)
- Platinum: 69 W/(mK)
Therefore, copper is the material with highest heat flow rate, so the metal which cools fastest.

Part 2) Which sample of copper demonstrates the greatest increase in temperature
To solve this part, we can have a look at how the amount of heat exchanged Q is related to the increase in temperature \Delta T:
Q=m C_S \Delta T
where m is the mass and Cs the specific heat of the material. Re-arranging the formula, we get
\Delta T= \frac{Q}{m C_s}
therefore, we see that the increase in temperature is inversely proportional to the mass m. This means that the block that will show the largest increase in temperature is the block with the smallest mass, so the correct answer is A) 0.5 kg.
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A piano tuner stretches a steel piano wire with a tension of 800 N. The steel wire is 0.400 m long and has a mass of 3.00 g. Wha
stepan [7]

Answer:

408.25 Hz.

Explanation:

The fundamental frequency of a stretched string is given as

f' = 1/2L√(T/m') .................... Equation 1

Note: The a steel piano wire is a string

Where f' = fundamental frequency of the wire, L = length of the wire, T = tension on the wire, m' = mass per unit length of the wire.

Given: L = 0.4 m, T = 800 N,

Also,

m' = m/L where m = mass of the steel wire = 3.00 g = 3/1000 = 0.003 kg.

L = 0.4 m

m' = 0.003/0.4 = 0.0075 kg/m.

Substituting into equation 1

f' = 1/(2×0.4)[√(800/0.0075)]

f' = 1/0.8[√(106666.67)]

f' = 326.599/0.8

f' = 408.25 Hz.

Hence the frequency of the fundamental mode of vibration = 408.25 Hz.

8 0
3 years ago
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skelet666 [1.2K]

Answer:

which question or just all?

Explanation:

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A cat falls from a table of height 1.3 m. What is the impact speed of the cat?
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Two small charged spheres are 7.59 cmcm apart. They are moved, and the force on each of them is found to have been tripled. How
tiny-mole [99]

Answer:

The two small charged spheres are now 4.382 cm apart

Explanation:

Given;

distance between the two small charged sphere, r = 7.59 cm

The force on each of the charged sphere can be calculated by applying Coulomb's law;

F = \frac{kq_1q_2}{r^2}

where;

F is the force on each sphere

q₁ and q₂ are the charges of the spheres

r is the distance between the spheres

F = \frac{kq_1q_2}{r^2} \\\\kq_1q_2 = Fr^2 \ \ (keep \ kq_1q_2 \ constant)\\\\F_1r_1^2 = F_2r_2^2\\\\r_2^2 = \frac{F_1r_1^2}{F_2} \\\\r_2 = \sqrt{\frac{F_1r_1^2}{F_2}} \\\\r_2 = r_1\sqrt{\frac{F_1}{F_2}}\\\\(r_1 = 7.59 \ cm, \ F_2 = 3F_1)\\\\r_2 =  7.59cm\sqrt{\frac{F_1}{3F_1}}\\\\r_2 =  7.59cm\sqrt{\frac{1}{3}}\\\\r_2 = 7.59cm *0.5773\\\\r_2 = 4.382 \ cm

Therefore, the two small charged spheres are now 4.382 cm apart.

4 0
3 years ago
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