Answer:9.75 m/s
Explanation:
Given
Length of ladder ![(L)=5 m](https://tex.z-dn.net/?f=%28L%29%3D5%20m)
Foot the ladder is moving away with speed of ![\frac{\mathrm{d} x}{\mathrm{d} t}=13 m/s](https://tex.z-dn.net/?f=%5Cfrac%7B%5Cmathrm%7Bd%7D%20x%7D%7B%5Cmathrm%7Bd%7D%20t%7D%3D13%20m%2Fs)
From diagram
------1
at ![x=3](https://tex.z-dn.net/?f=x%3D3%20)
![y^2=25-9=16](https://tex.z-dn.net/?f=y%5E2%3D25-9%3D16)
![y=4 m](https://tex.z-dn.net/?f=y%3D4%20m)
Now differentiating equation 1 w.r.t time
![2x\frac{\mathrm{d} x}{\mathrm{d} t}+2y\frac{\mathrm{d} y}{\mathrm{d} t}=0](https://tex.z-dn.net/?f=2x%5Cfrac%7B%5Cmathrm%7Bd%7D%20x%7D%7B%5Cmathrm%7Bd%7D%20t%7D%2B2y%5Cfrac%7B%5Cmathrm%7Bd%7D%20y%7D%7B%5Cmathrm%7Bd%7D%20t%7D%3D0)
![x\frac{\mathrm{d} x}{\mathrm{d} t}=-y\frac{\mathrm{d} y}{\mathrm{d} t}](https://tex.z-dn.net/?f=x%5Cfrac%7B%5Cmathrm%7Bd%7D%20x%7D%7B%5Cmathrm%7Bd%7D%20t%7D%3D-y%5Cfrac%7B%5Cmathrm%7Bd%7D%20y%7D%7B%5Cmathrm%7Bd%7D%20t%7D)
![3\times 13=-4\times \frac{\mathrm{d} y}{\mathrm{d} t}](https://tex.z-dn.net/?f=3%5Ctimes%2013%3D-4%5Ctimes%20%5Cfrac%7B%5Cmathrm%7Bd%7D%20y%7D%7B%5Cmathrm%7Bd%7D%20t%7D)
![\frac{\mathrm{d} y}{\mathrm{d} t}=-\frac{3\times 13}{4}=-9.75 m/s](https://tex.z-dn.net/?f=%5Cfrac%7B%5Cmathrm%7Bd%7D%20y%7D%7B%5Cmathrm%7Bd%7D%20t%7D%3D-%5Cfrac%7B3%5Ctimes%2013%7D%7B4%7D%3D-9.75%20m%2Fs)
negative indicates distance is decreasing with time
Answer:
)Give the definition of poverty line as defined by the World Bank.
Answer: See photo
Explanation: There are a couple of ways to use velocity in an equation in the photo.
Correct choices are marked in bold:
travel in straight lines and can bounce off surfaces --> TRUE, normally electromagnetic waves travel in straight lines, however they can be reflected by objects, bouncing off their surfaces
travel through space at the speed of light --> TRUE, all electromagnetic waves in space (vacuum) travel at the speed of light,
)
travel only through matter --> FALSE; electromagnetic waves can also travel through vacuum
travel only through space --> FALSE, electromagnetic waves can also travel through matter
can bend around objects --> TRUE, this is what happens for instance when diffraction occurs: electromagnetic waves are bended around obstacles or small slits
move by particles bumping into each other --> FALSE, electromagnetic waves are oscillations of electric and magnetic fields, so no particles are involved
move by the interaction between an electric field and a magnetic field --> TRUE, electromagnetic waves consist of an electric field and a magnetic field oscillating in a direction perpendicular to the direction of motion of the wave