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3 years ago

Coal as a fuel source led to the invention of

Physics

1 answer:

Ludmilka [50]3 years ago

8 0

Answer:

coal as a fuel source led to the invention of the printing press i think

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A motorcyclist drove 7 km at 57km/h and then another 7 km at 81 km/h. What was the average speed?

alex41 [277]

Answer:

The average speed of the car is 66.9 km/h

Explanation:

Here distance covered with the speed 57 km/h=7 km 

distance covered with the speed of 81 km/h=7 km

Average speed is equal to the ratio of total distance to the total time.

total distance= 7 + 7= 14 km

$time= \frac{distance}{speed}$

time taken to cover the first 7 km= 7/57 h

time taken to cover the second part of the journey = 7/81 h

average speed = $14/(7/57+7/81)=(14 \times 57 \times 81)/945=66.9 km/h$ 

Shortcut: 

When equal distances are covered with different speeds average speed=2 ab/(a+b) where a and b are the variable speeds in the phases. 

7 0

3 years ago

Can a body have constant speed and still be acclerating ? Give an Example

Allushta [10]

Hi Pupil Here's Your answer :::

➡➡➡➡➡➡➡➡➡➡➡➡➡

An object moving with constant speed can be accelerated if direction of motion changes. For example, an object moving with a constant speed in a circular path has an acceleration because its direction of motion changes continuously.

⬅⬅⬅⬅⬅⬅⬅⬅⬅⬅⬅⬅⬅

Hope this Helps . . . . . . . . .

3 0

3 years ago

The tuning fork has a frequency of 426.7 is found to cause resonance in a closed column of air measuring 0.186 (the diameter of

lidiya [134]

Answer:

The velocity of the tuning fork sound is 317.4648 m/s

Explanation:

The given parameters are;

The frequency of the fork, f = 426.7 Hz

The length of the closed air column, L = 0.186 m

The diameter of the tube, d = 0.15 m

At the fundamental frequency in a closed tube, we have;

λ = 4·L

Where;

λ = The wavelength of the wave

L = The length of the tube

From the equation for the velocity of a wave, we have;

v = f·λ

Where;

v = The velocity of the (sound) wave

f = The frequency of the wave = 426.7 Hz

λ = 4·L = 4 × 0.186 m = 0.744 m

∴ v = 426.7 Hz × 0.744 m = 317.4648 m/s

Therefore, the velocity of the sound produced by the tuning fork, v = 317.4648 m/s

3 0

3 years ago

The sound intensity at a distance 2.00 m from a sound source is 5.00 Find the total sound energy emitted by the source in each s

notka56 [123]

Answer:

P = 251, 3 W

Explanation:

The intensity is defined as the power emitted per unit area

I = P / A

Since sound is distributed in all directions spherical shape, the area of a sphere is

A = 4π r²

let's clear the power and replace

P = I A

P = I (4π r²)

let's calculate

P = 5.00 (4π 2²)

P = 251, 3 W

6 0

3 years ago

A cello string 0.75 m long has a 220 hz fundamental frequency. find the wave speed along the vibrating string. answer in units o

maxonik [38]

For fundamental frequency of a string to occur, the length of the string has to be half the wavelength. That is,

1/2y = L, where L = length of the string, y = wavelength.

Therefore,
y = 2L = 2*0.75 =1.5 m

Additionally,
y = v/f Where v = wave speed, and f = ferquncy

Then,
v = y*f = 1.5*220 = 330 m/s

4 0

3 years ago