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Makovka662 [10]
3 years ago
6

An elevator of massmis initially at rest onthe first floor of a building. It moves upward,and passes the second and third floors

witha constant velocity, and finally stops at thefourth floor.The distance between adjacentfloors is h.What is the net work done on the elevatorduring the entire trip, from the first floor tothe fourth floor?
1. None of these.
2. W=-3m g h
3. W=-4m g h
4. W= 3m g h
5. W= 0correct
6. W= 4m g h
Physics
1 answer:
Varvara68 [4.7K]3 years ago
7 0

To solve this problem it is necessary to apply the concepts of Work. Work is understood as the force applied to travel a determined distance, in this case the height. The force in turn can be expressed by Newton's second law as the ratio between mass and gravity, as well

W = mgh

Where,

m = mass

h = height

g = Gravitational constant

When it ascends to the second floor it has traveled the energy necessary to climb a height, under this logic, until the 4 floor has traveled 3 times the height h of each of the floors therefore

h = 3h

Replacing in our equation we have to

W = mgh\\W = mg(3h)\\W = 3mgh

The correct answer is 4.

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Answer:

The temperature of silver at this given resistivity is 2971.1 ⁰C

Explanation:

The resistivity of silver is calculated as follows;

R_t = R_o[1 + \alpha(T-T_o)]\\\\

where;

Rt is the resistivity of silver at the given temperature

Ro is the resistivity of silver at room temperature

α is the temperature coefficient of resistance

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T is the temperature at which the resistivity of silver will be two times the resistivity of iron at room temperature

R_t = R_o[1 + \alpha(T-T_o)]\\\\\R_t = 1.59*10^{-8}[1 + 0.0038(T-20)]

Resistivity of iron at room temperature = 9.71 x 10⁻⁸ ohm.m

When silver's resistivity becomes 2 times the resistivity of iron, we will have the following equations;

R_t,_{silver} = 2R_o,_{iron}\\\\1.59*10^{-8}[1 + 0.0038(T-20)] =(2 *9.71*10^{-8})\\\\\ \ (divide \ through \ by \ 1.59*10^{-8})\\\\1 + 0.0038(T-20) = 12.214\\\\1 + 0.0038T - 0.076 = 12.214\\\\0.0038T +0.924 = 12.214\\\\0.0038T  = 12.214 - 0.924\\\\0.0038T = 11.29\\\\T = \frac{11.29}{0.0038} \\\\T = 2971.1 \ ^0C

Therefore, the temperature of silver at this given resistivity is 2971.1 ⁰C

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