help me w mine and ill try to help with yours
"Pluto was the first dwarf planet to be discovered" is the one statement among the following choices given in the question that is true <span>about dwarf planets. The correct option among all the options that are given in the question is the first option or option "a". Pluto was classified as a planet at first but in the year 1930 it was classified as a dwarf planet.</span>
Answer:
B
Explanation:
because atoms make up an element.
Energy can not be created or destroyed but can change from one form to another.
example: as a roller coaster cart loses height the more speed it gains, the potential energy is transferred into kenetic energy
Answer:
![S_a_v_e_r_a_g_e=48km/h](https://tex.z-dn.net/?f=S_a_v_e_r_a_g_e%3D48km%2Fh)
Explanation:
Ok, the average speed can be calculate with the next equation:
(1)
Basically the car cover the same distance "d" two times, but at different speeds, so:
![Total\hspace{3}distance=2*d](https://tex.z-dn.net/?f=Total%5Chspace%7B3%7Ddistance%3D2%2Ad)
and the total time would be the time t1 required to go from A to B plus the time t2 required to go back from B to A:
![Total\hspace{3}time=t1+t2](https://tex.z-dn.net/?f=Total%5Chspace%7B3%7Dtime%3Dt1%2Bt2)
From basic physics we know:
![t=\frac{d}{S1}](https://tex.z-dn.net/?f=t%3D%5Cfrac%7Bd%7D%7BS1%7D)
so:
![t1=\frac{d}{S1}](https://tex.z-dn.net/?f=t1%3D%5Cfrac%7Bd%7D%7BS1%7D)
![t2=\frac{d}{S2}](https://tex.z-dn.net/?f=t2%3D%5Cfrac%7Bd%7D%7BS2%7D)
Using the previous information in equation (1)
![S_a_v_e_r_a_g_e=\frac{2*d}{\frac{d}{S1} +\frac{d}{S2} }=\frac{2*d}{\frac{d*S2+d*S1}{S1+S2} }](https://tex.z-dn.net/?f=S_a_v_e_r_a_g_e%3D%5Cfrac%7B2%2Ad%7D%7B%5Cfrac%7Bd%7D%7BS1%7D%20%2B%5Cfrac%7Bd%7D%7BS2%7D%20%7D%3D%5Cfrac%7B2%2Ad%7D%7B%5Cfrac%7Bd%2AS2%2Bd%2AS1%7D%7BS1%2BS2%7D%20%7D)
Factoring:
(2)
Finally, replacing the data in (2)
![S_a_v_e_r_a_g_e=\frac{2*40*60}{60+40} =48km/h](https://tex.z-dn.net/?f=S_a_v_e_r_a_g_e%3D%5Cfrac%7B2%2A40%2A60%7D%7B60%2B40%7D%20%3D48km%2Fh)