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Mars2501 [29]
4 years ago
8

How many Joules of potential

Physics
1 answer:
s2008m [1.1K]4 years ago
4 0

Answer:

40 j, 80j.

Explanation:

P.E= mgh. G=10 m/s².

For 4m, P.E=1*10*4=40 joules.

For 8m, P.E=1*10*8=80 joules.

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A car accelerates uniformly in a straight line
Alinara [238K]

Recall that

{v_f}^2={v_i}^2=2a\Delta x

The car starts from rest, so v_i=0, and we get

{v_f}^2=2\left(2.8\dfrac{\rm m}{\mathrm s^2}\right)(69\,\mathrm m)\implies v_f\approx19.66\dfrac{\rm m}{\rm s}

4 0
3 years ago
A cup of hot coffee initially at 95 degrees C cools to 80 degrees C in 5 min while sitting in a room of temperature 21 degrees C
Oksana_A [137]

Answer:

When the temperature of the coffee is 50 °C, the time will be 20.68 mins

Explanation:

Given;

The initial temperature of the coffee T₀ = 95 °C

The temperature of the room = 21°C

Let T be the temperature at time of cooling t in mins

According to Newton's law of cooling;

\frac{dT}{dt} \alpha (T-21)\\\\\frac{dT}{dt} = k (T-21)\\\\\frac{dT}{T-21} = kdt\\\\\int\limits {\frac{dT}{T-21}}  =  \int\limits kdt\\\\Log(T-21) =kt +  Logc \\\\Log (\frac{T-21}{c} ) = kt\\\\T -21 = ce^{kt}\\\\At \ t = 0, T = 95\\\\95-21 = ce^0\\\\74 = c\\\\New, equation: T -21 = 74e^{kt}\\\\Again; when \ t= 5\ min, T = 80\\\\80 -21 = 74e^{5k}\\\\59 = 74e^{5k}\\\\e^{5k} = \frac{59}{74}\\\\ 5k = ln(\frac{59}{74})\\\\5k = -0.2265\\\\k = -0.0453

When the temperature is 50 °C, the time t in min is calculated as;

T -21 = 74e^{-0.0453t}\\\\50 -21 = 74e^{-0.0453t}\\\\29 = 74e^{-0.0453t}\\\\\frac{29}{74} = e^{-0.0453t}\\\\0.39189 = e^{-0.0453t}\\\\ln(0.39189 ) = {-0.0453t}\\\\-0.93677 = {-0.0453t}\\\\t = \frac{-0.93677}{-0.0453}\\\\ t = 20.68 \ mins

Therefore, when the temperature of the coffee is 50 °C, the time will be 20.68 mins

4 0
3 years ago
A radioactive substance decays at an annual rate of 131313 percent. If the initial amount of the substance is 325325325 grams, w
anyanavicka [17]

Answer: f_{(t)}=325(0.87)^{t}

Explanation:

If we have an initial amount of a radioactive material or substance, which is 325g,  and we also are told this amount decays 13\% each year, this means each year 87\% of the substance remains:

100\%-13\%=87\%=0.87

<u />

<u>To understand it better:</u>

Year 1: 325(87\%)=325(0.87)

Year 2: 325(0.87)(0.87)=325(0.87)^{2}

Year 3: 325(0.87)(0.87)(0.87)=325(0.87)^{3}

and so on until year t:

Year t: 325(0.87)^{t}

Therefore, the function tha best describes this radiation decay situation is:

f_{(t)}=325(0.87)^{t}

4 0
3 years ago
If a projectile travels in the air for 8 seconds when does a projectile reach its highest point
emmainna [20.7K]

Given

The projectile is in air for a time of t=8 sec

To find

The time it takes to reach the highest point

Explanation

A projectile moves up to the highest point and then again moves down following a parabolic path.

So it will reach the highest point at a time half the time it requires to follow teh parabolic path.

The time taken to reach the highest point is 4 sec

Conclusion

The time taken is 4 sec.

5 0
2 years ago
Which dynamic sign indicates very loud?
Pavel [41]
(ff) fortissimo means very loud
3 0
4 years ago
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