Answer:

Explanation:
Given,
The angle of the slide=
The mass of the child is= m
coefficient of friction = 0.20
when she slides down now apply Newton's law


therefore the acceleration

![a=g[\sin \theta -\mu \cos \theta]](https://tex.z-dn.net/?f=a%3Dg%5B%5Csin%20%5Ctheta%20-%5Cmu%20%5Ccos%20%5Ctheta%5D)
![a=9.8\times [\sin 42^\circ -0.2\times \cos 42^\circ]](https://tex.z-dn.net/?f=a%3D9.8%5Ctimes%20%5B%5Csin%2042%5E%5Ccirc%20-0.2%5Ctimes%20%5Ccos%2042%5E%5Ccirc%5D)

hence, the magnitude of acceleration during her sliding is equal to 
The work done is 400 J
Explanation:
The work done by you in pushing the box along the slope is given by

where
F is the magnitude of the force applied
d is the distance covered by the box along the slope
Here we have the following:
F = 200 N is the magnitude of the force applied
is the distance covered, where
h = 1 m is the vertical rise
is the slope of the plane
Substituting and solving, we find

Learn more about work:
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Explanation:
Loudness of sound is a measure of response of sound to our ear. Loudness of sound is not simply the energy reaching the human ear, but it also tells about the sensitivity of human ear detecting this energy. Loudness of sound is measured in decibel (dB). As energy reaching the ear depends on square of amplitude, loudness of sound depends on various factors namely,
(i) Amplitude of sound waves
(ii) Sensitivity of ear
(iii) Distance from the source of the sound and the listener.
Vt = Vboat - Vriver
Vt = 18 - 2.5 = 15.5 m/s
If the boat's direction is the same as the water, you sum the velocities of the river and the boat .
A) initial volume
We can calculate the initial volume of the gas by using the ideal gas law:

where

is the initial pressure of the gas

is the initial volume of the gas

is the number of moles

is the gas constant

is the initial temperature of the gas
By re-arranging this equation, we can find

:

2) Now the gas cools down to a temperature of

while the pressure is kept constant:

, so we can use again the ideal gas law to find the new volume of the gas

3) In a process at constant pressure, the work done by the gas is equal to the product between the pressure and the difference of volume:

by using the data we found at point 1) and 2), we find

where the negative sign means the work is done by the surrounding on the gas.