5.85 m/s accelerates at 2.35m/s for 3.25s

Eva is in a closed, dark room. She uses her arm muscles to turn on a lamp. When she moves her hand closer to the lamp, the light

12345 [234]

Well, we know that the total energy in a closed system remains constant.

The problem with the story of Eva is that she is not in a closed system.
If the dark room were really a closed system, then she could press the
button or turn the switch all day, and the lamp could not light. It needs
electrical energy coming in from somewhere in order to turn on.

Let's say that Eva used her arm muscles to strike a match and light the
candle on the table. Then we would have have food energy, muscle
energy, chemical energy in the match, chemical energy in the candle,
heat and light energy coming out of the candle, heat energy soaking into
her hand, light energy bouncing off of the book and into her eyes ... all
going on during the story, and the sum total of all of them would remain
constant.

4 0

4 years ago

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An object is realsed From rest . how far does it fall during the second second of fall?

Savatey [412]

Answer:

14.715 m

Explanation:

Assume that the acceleration due to gravity is 9.81 m/s^2 downwards, take downwards as positive

First second:

v = u + at

v = 9.81 m/s

Second second:

s = ut + (1/2)at^2

s = 9.81(1) + (1/2)(9.81)(1)^2

s = 14.715 m

6 0

3 years ago

A car with two people traveling down the road has a mass of 100 kg and a velocity of 5 m/s. The car pulls over and picks up two

Oliga [24]

Answer:

750 kg.m/s

Explanation:

Momentum is the product of mass and velocity in kg.m/s.

In this case, initial momentum⇒p=m × v where m is mass and v is velocity

initial mass of car m₁=100 kg

Initial velocity of car v₁=5 m/s

Initial momentum= 100×5= 500 kg.m/s

New mass after picking two extra people m₂= 150 kg

Velocity stays the same v₂=v₁= 5 m/s

New momentum= m₂× v₂

p=150×5=750 kg.m/s

4 0

3 years ago

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By what factor is the intensity of sound at a rock concert louder than that of a whisper when the two intensity levels are 120 d

lyudmila [28]

Answer:

d) $7.94\times 10^{9}$

Explanation:

β₁ = sound level of sound at rock concert = 120 dB

β₂ = sound level of sound due to whisper = 21 dB

I₁ = Intensity of sound at rock concert

I₂ = Intensity of sound due to whisper

sound level of sound at rock concert is given as

$\beta _{1} = 10 log\left ( \frac{I_{1}}{10^{-12}} \right )$

$120 = 10 log\left ( \frac{I_{1}}{10^{-12}} \right )$

$12 = log\left ( \frac{I_{1}}{10^{-12}} \right )$ Eq-1

sound level due to whisper is given as

$\beta _{2} = 10 log\left ( \frac{I_{2}}{10^{-12}} \right )$

$21 = 10 log\left ( \frac{I_{2}}{10^{-12}} \right )$

$2.1 = log\left ( \frac{I_{2}}{10^{-12}} \right )$ Eq-2

subtracting Eq-2 from Eq-1

$12 - 2.1 = log\left ( \frac{I_{1}}{10^{-12}} \right ) - log\left ( \frac{I_{2}}{10^{-12}} \right )$

$9.9 = log\left ( \frac{I_{1}}{I_{2}} \right )$

$\left ( \frac{I_{1}}{I_{2}} \right ) = 7.94\times 10^{9}$

6 0

3 years ago

A certain gasoline engine has an efficiency of 35.3%. What would the hot reservoir temperature be for a Carnot engine having tha

levacccp [35]

Answer:

The temperature of hot reservoir is 669.24 K.

Explanation:

It is given that,

Efficiency of gasoline engine, $\eta=35.3\%=0.353$

Temperature of cold reservoir, $T_C=160^{\circ}C=433\ K$

We need to find the temperature of hot reservoir. The efficiency of Carnot engine is given by :

$\eta=1-\dfrac{T_C}{T_H}$

$T_H=\dfrac{T_C}{1-\eta}$

$T_H=\dfrac{433}{1-0.353}$

$T_H=669.24\ K$

So, the temperature of hot reservoir is 669.24 K. Hence, this is the required solution.

4 0

3 years ago