Answer:
4
Explanation:
It has 8 O atoms and 4 O2(g) molecules
It is a concave lens
Have a nice day
In this experiment, the independent variable is the surface, the dependant variable is the distance one end of the surface must be lifted to see movement of the object, and the control variable is the object. Since the surface height at one end is changed and the object is kept the same, the only conclusion that can be made is whether the surface has an effect on the force of friction. Of course, basic physics tells you that it does, therefore A is correct.
Here in the above situation when boy pushes the girl there will be equal and opposite force on boy as per Newton's III law.
Due to this action reaction law boy will also go back with some speed.
Since there is no external force on this girl + boy system so we can use momentum conservation principle here.
As per momentum conservation
![m_1v_{1i} + m_2v_{2i} = m_1v_{1f} + m_2v_{2f}](https://tex.z-dn.net/?f=m_1v_%7B1i%7D%20%2B%20m_2v_%7B2i%7D%20%3D%20m_1v_%7B1f%7D%20%2B%20m_2v_%7B2f%7D)
![60*0 + 40*0 = 60*v_{1f} + 40*0.3](https://tex.z-dn.net/?f=60%2A0%20%2B%2040%2A0%20%3D%2060%2Av_%7B1f%7D%20%2B%2040%2A0.3)
![0 = 60*v_{1f}+ 12](https://tex.z-dn.net/?f=0%20%3D%2060%2Av_%7B1f%7D%2B%2012)
![v_{1f} = -0.2 m/s](https://tex.z-dn.net/?f=v_%7B1f%7D%20%3D%20-0.2%20m%2Fs)
So boy will go back with speed 0.2 m/s
Part b)
Since the boy and girl will always exert same force on each other by Newton's III law so it has no it matter whether the boy pushed the girl, the girl pushed the boy, or they put their hands together and pushed each other away.
As in all above cases the as per Newton's III law the force on them is always equal and opposite.
Answer:
Explanation:
Given
coefficient of kinetic friction
=0.34
inclination ![\theta =44](https://tex.z-dn.net/?f=%5Ctheta%20%3D44)
weight of block=51 N
(a) When block is moving upward friction force acts downward
thus
![Fsin\theta -W-f_r=0](https://tex.z-dn.net/?f=Fsin%5Ctheta%20-W-f_r%3D0)
as block is moving with constant velocity thus
is zero
![f_r=\mu _kN=0.34\times Fcos\theta](https://tex.z-dn.net/?f=f_r%3D%5Cmu%20_kN%3D0.34%5Ctimes%20Fcos%5Ctheta%20)
![F\left ( \sin \theta -\mu \cos \theta \right )=W](https://tex.z-dn.net/?f=F%5Cleft%20%28%20%5Csin%20%5Ctheta%20-%5Cmu%20%5Ccos%20%5Ctheta%20%5Cright%20%29%3DW)
![F=\frac{51}{0.45}=113.31 N](https://tex.z-dn.net/?f=F%3D%5Cfrac%7B51%7D%7B0.45%7D%3D113.31%20N)
(b)When Block slides down the wall friction changes its direction to oppose the block
![Fsin\theta -W+f_r=0](https://tex.z-dn.net/?f=Fsin%5Ctheta%20-W%2Bf_r%3D0)
![F\left ( \sin \theta +\mu \cos \theta \right )=W](https://tex.z-dn.net/?f=F%5Cleft%20%28%20%5Csin%20%5Ctheta%20%2B%5Cmu%20%5Ccos%20%5Ctheta%20%5Cright%20%29%3DW)
![F=\frac{W}{\left ( \sin \theta +\mu \cos \theta \right )}](https://tex.z-dn.net/?f=F%3D%5Cfrac%7BW%7D%7B%5Cleft%20%28%20%5Csin%20%5Ctheta%20%2B%5Cmu%20%5Ccos%20%5Ctheta%20%5Cright%20%29%7D)
![F=\frac{51}{0.939}=54.299 N](https://tex.z-dn.net/?f=F%3D%5Cfrac%7B51%7D%7B0.939%7D%3D54.299%20N)