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3 years ago

Calculate the rate constant for the first-order decay of 24na (t1/2 = 14.7 h).

1 answer:

6 0

This problem is pretty straight forward since we are given the half time and we simply have to find for the rate constant. The equation relating the two variable is:

t1/2 = ln(2) / k

where k is the rate constant, therefore:

k = ln(2) / t1/2

k = ln(2) / 14.7 h

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Consider a resonator with ω0 = 100 rad/sec and a Q factor of 100. Calculate the time takes it to settle within 2% of the final v

Alla [95]

Answer:

8 s

Explanation:

Damping factor, F is given by

$F=\frac {1}{2Q}$ where Q is quality factor

Also, we know that the settling time, T is given by

$T=\frac {4}{FW}$ where W is the resonant frequency.and substituting the first equation here we get

$T= \frac {4\times 2Q}{W}$

Since it takes 2% of final value to settle and considering 100 rad/s for resonant frequency and taking quality factor of 100 then

$T=\frac {4\times 2\times 100}{100}= 8 s$

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3 years ago

Which statement describes a characteristic of a question that can be answered through scientific inquiry? A. It can be answered

saw5 [17]

Answer:

the correct one is D

Explanation:

A question that can be answered with a scientific investigation must be a question where measurements of some kind can be made and with these measurements check that the question is correct or not.

When examining the answers the correct one is D

7 0

3 years ago

Describe the process of electricity generation and the efficiency and economics of it

Mrac [35]

Answer:

The process of producing electric energy or the amount of electric energy produced by transforming other forms of energy into electrical energy; commonly expressed in kilowatt-hours (kWh) or megawatt-hours (MWh). Electric power plant efficiency η is defined as the ratio between the useful electricity output from the generating unit, in a specific time, and the energy value of the energy source supplied to the unit in the same time period. For electricity generation based on steam turbines 65% of all prime energy is wasted as heat. The maximum theoretical energy efficiency is defined in more detail by the Rankine cycle. For modern practical systems this is about 40% but less for older generating plant. The efficiency falls still further if fuels with lower energy content such as biomass are used to supply the plant. The economics of power generation based on reciprocating engines depends to a large extent on the use to which the engine is to be put. The cheapest engines available are small petrol-driven engines based on car engines, which are manufactured in large numbers each year.

Explanation:

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3 years ago

A 20 kg box on a horizontal frictionless surface is moving to the right at a speed of 4.0 m/s. The box hits and remains attached

yanalaym [24]

Answer:

Work done by the spring is negative

Explanation:

We can answer this question by thinking what is the force acting on the box.

In fact, the force acting on the box is the restoring force of the spring, which is given by Hooke's Law:

$F=-kx$

where

k is the spring constant

x is the displacement of the box with respect to the equilibrium position of the spring

The negative sign in the equation indicates that the direction of the force is always opposite to the direction of the displacement: so, whether the spring is compressed or stretched, the force applied by the spring on the box is towards the equilibrium position.

The work done by the restoring force is also given by

$W=Fx cos \theta$

where

F is the restoring force

x is the displacement

$\theta$ is the angle between the direction of the force and the displacement

Here we know that the force is always opposite to the displacement, so

$\theta=180^{\circ} \rightarrow cos \theta =-1$

Which means that the work done by the spring is always negative, since the direction of the restoring force is always opposite to the direction of motion.

7 0

3 years ago

A furniture shop refinishes chairs. Employees use one of two methods to refinish each chair. Method I takes 0.5 hours and the ma

satela [25.4K]

Answer:

method I = 88 chairs

method II = 62 chairs

Explanation:

This problem can be modeled by a system of two linear equations.

Define x as the number of chairs refinished by method I and y by method II

The sum of hours spent on both methods should equal 199 and the sum of total material cost should equal $1226, therefore:

$0.5x + 2.5y = 199$