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3 years ago

Complete the following statement: today, the standard unit of time is defined in terms of

Physics

1 answer:

natima [27]3 years ago

6 0

Today, the standard unit of time is defined in terms of <span>electromagnetic waves emitted by cesium atoms.</span>

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Maru [420]

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3 years ago

Stars produce their own light but planets do not. Even then we can see them. explain

PilotLPTM [1.2K]

Planets are not hot enough, and that's because they lack the internal energy sources that stars have: thermonuclear fusion (They do emit a little light, mainly infrared light, but nothing compared to the sun)

Planets don't have their own light, so simply they do not emit light, this phenomena goes back to their information. When they are formed, they are much, much less hotter than the stars. In stars, fusion reaction always goes on, in which energy, as well as light is formed, so, there is light for stars to emit for a long time.

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4 years ago

Using the standard convention "positive is up", what is the sign of the acceleration of a rock you throw up (a) as it is going u

Sonbull [250]

Answer:

(a) Negative

(b) Positive

Explanation:

Here is a question on sign.

(a) When the rock is going up, it is working against gravity. In this case, the acceleration due to gravity will take a negative value. This is because gravity works or acts downwards

(b) When the rock is coming down, it is actually working with gravity. So in this case, the sign will ne positive

7 0

3 years ago

If the plant produces electric energy at the rate of 1. 5 gw , how much exhaust heat is discharged per hour?

expeople1 [14]

The amount of exhaust heat discharged per hour from the plant which produces electric energy at the rate of 1. 5 gw, is 9.36×10¹⁹ J/h.

<h3>How to calculate the heat discharged per hour?</h3>

The heat is discharged per hour is equal to the different of total power and actual power.

The plant produces electric energy at the rate of 1. 5 gw. Let assume the efficiency of this power plant is 64% between the temperature of 660 degree C to 330 degree Celsius.

Thus, the maximum efficiency is,

$\eta_{max}=1-\dfrac{660+273}{330+273}\\\eta_{max}=0.55$

The total power is,

$P_t=\dfrac{P_A}{\eta_{max}\times0.64}\\P_t=\dfrac{1.5}{0.55\times0.64}\\P_t=4.26\rm\; GW$

Thus, the heat discharged per hour is,

$Q=4.26-1.5\\Q=2.76\text{GW}\\$

Multiply the value with 3600 to convert it in s/h,

$Q=2.76\times10^9\times3600\text{ J/h}\\Q=9.36\times10^{19}\text{ J/h}\\$

Thus, the amount of exhaust heat discharged per hour from the plant which produces electric energy at the rate of 1. 5 gw, is 9.36×10¹⁹ J/h.

Learn more about the heat discharged per hour here;

brainly.com/question/19666326

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6 0

2 years ago

A high-jump athlete leaves the ground, lifting her center of mass 1.8 m and crossing the bar with a horizontal velocity of 1.4 m

Romashka [77]

Answer:

The minimum speed when she leave the ground is 6.10 m/s.

Explanation:

Given that,

Horizontal velocity = 1.4 m/s