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3 years ago

I Do you guys think people used energy before the modern times? Why or why not?

Physics

1 answer:

zepelin [54]3 years ago

3 0

Answer:

do you mean before we used fossil fuels? steam.before steam? fire was used for like ...125,000 years ago. we were not smart back then but we were smart enough.

Explanation:

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Two train whistles have identical frequencies of 180 Hz. When one train is at rest in the station and the other is moving nearby

Ierofanga [76]

Answer:

-3.77 m/s

3.85 m/s

Explanation:

given that

Frequency at stationary = 180 Hz

Beat frequency = 2 Hz

Using Doppler effect, we know that

f' = f[(v ± v0) / (v ± vs)], where

v = speed of sound, 343 m/s

v0 = speed of the observer, 0

vs = speed of light, ?

f = stationary frequency, 180 Hz

f' = stationary ± beat frequency, 180 ± 2

Applying the formula, we have

f' = f[(v ± v0) / (v ± vs)]

182 = 180 [(343 + 0) / (343 + vs)]

182/180 = 343 / 343 + vs

343 + vs = 343 * 180/182

343 + vs = 339.23

vs = 339.23 - 343

vs = -3.77 m/s

Again, using

f' = f[(v ± v0) / (v ± vs)]

178 = 180 [(343 + 0) / (343 + vs)]

178/180 = 343 / 343 + vs

343 + vs = 343 * 180/178

343+ vs = 346.85

vs = 346.85 - 343

vs = 3.85 m/s

7 0

3 years ago

A dock worker loading crates on a ship finds that a 27 kg crate, initially at rest on a horizontal surface, requires a 80 N hori

Aleksandr-060686 [28]

Answer:0.302

Explanation:

Given

mass of crate m=27 kg

Force required to set crate in motion is 80 N

Once the crate is set in motion 56 N is require to move it with constant velocity

i.e. 80 N is the amount of force needed to just overcome static friction and 56 is the kinetic friction force

thus

$f_s(static\ friction)=\mu \cdot N$

where $\mu$ is the coefficient of static friction and N is Normal reaction

$N=mg$

$f_s=\mu mg$

$\mu mg=80$

$\mu =\frac{80}{27\times 9.8}$

$\mu =0.302$

7 0

4 years ago

Which of these waves probably has the largest wavelength?

elena-14-01-66 [18.8K]

Answer:

I think it's the last one

Explanation:

good luck

5 0

4 years ago

Read 2 more answers

A box with mass m = 8 kg is pushed x = 10 m across a level floor by a constant applied force F P = 16.27 N. The coefficient of k

vitfil [10]

Answer:

Final speed of the box after it has moved to x = 10 is given as

v = 3.35 m/s

Explanation:

As we know by work energy theorem that work done by all the forces is equal to the change in its kinetic energy

Here work done by external force + work done by friction = change in kinetic energy of the box

so we have

$W_{ex} + W_{fric} = \frac{1}{2}mv^2$

$F x - \mu mg x = \frac{1]{2}mv^2$

$16.27 (10) - (0.15)(8)(9.8) (10) = \frac{1}{2}(8) v^2$

$162.7 - 117.6 = 4 v^2$

$v = 3.35 m/s$

4 0

3 years ago

I need Help ASAP, and actually help, not just for the points.

UNO [17]

Answer:

750 force

Explanation:

I have never worked with force but I can guess using the formula. 1500, which is the mass, multiplied by the acceleration, 0.5, would equal 750 force, if being applied by the equation listed, Force= mass×acceleration

7 0

3 years ago

Read 2 more answers