Waves carry energy from one place to another. Because waves carry energy, some waves are used for communication, eg radio and television waves and mobile telephone signals. ... Some types of waves need to be transmitted through matter, either a solid, liquid or a gas. For example, water waves have to travel in water.
The subscript after the element indicates the number of atoms of that element in the molecule. So, in H20, the subscript after the H, which stands for hydrogen, is 2. This means that there are 2 hydrogen atoms in a water molecule.
Hope this helps! :)
The answer is B. Friction is going to the RIGHT because friction works against where you are trying to go
Wee can use here kinematics
as we know that
![y = v*t + \frac{1}{2} at^2](https://tex.z-dn.net/?f=y%20%3D%20v%2At%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20at%5E2)
for shorter tree we know that
![y = 0 + \frac{1}{2}*9.8 * 2^2](https://tex.z-dn.net/?f=y%20%3D%200%20%2B%20%5Cfrac%7B1%7D%7B2%7D%2A9.8%20%2A%202%5E2)
![y = 19.6 meter](https://tex.z-dn.net/?f=y%20%3D%2019.6%20meter)
now since we know that other tree is twice high
So height of other tree is y = 39.2 m
now again by above equation
![y = v*t + \frac{1}{2} at^2](https://tex.z-dn.net/?f=y%20%3D%20v%2At%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20at%5E2)
![39.2 = 0 + \frac{1}{2}*9.8 * t^2](https://tex.z-dn.net/?f=39.2%20%3D%200%20%2B%20%5Cfrac%7B1%7D%7B2%7D%2A9.8%20%2A%20t%5E2)
![t = 2.83 s](https://tex.z-dn.net/?f=t%20%3D%202.83%20s)
so the time taken is 2.83 s