apple, earth. earth more massive than moon. astronauts showed this - armstrong etc
The velocity vector of the planet points toward the center of the circle is the following is true about a planet orbiting a star in uniform circular motion.
A. The velocity vector of the planet points toward the center of the circle.
<u>Explanation:</u>
Motion of the planet around the star is mentioned to be uniform and around a circular path. Objects in uniform circular motion motion has constant angular speed but the velocity of the object will not remain constant. Since the planet is in circular motion the direction of velocity vector at a particular point is tangential to the circular path at that particular point.
Thus at every point, the direction of velocity vector changes and this means the velocity is never constant. The objects in uniform circular motion has centripetal acceleration which means that velocity vector of the planet points toward the center of the circle.
Material medium electric waves
Answer : The final energy of the system if the initial energy was 2000 J is, 3500 J
Solution :
(1) The equation used is,

where,
= final internal energy
= initial internal energy
q = heat energy
w = work done
(2) The known variables are, q, w and 
initial internal energy =
= 2000 J
heat energy = q = 1000 J
work done = w = 500 J
(3) Now plug the numbers into the equation, we get

(4) By solving the terms, we get




(5) Therefore, the final energy of the system if the initial energy was 2000 J is, 3500 J
A watering can is used to hold a water that we will use to water the plants. The water has both mass and volume. Two watering cans are most often different by the volume they contain.
Many various units for volume are used but most often used unit is liter. In a metric system basic units are those such as meter, kilogram and liter while in imperial system units used are those such as foote, inch, pound and gallon.
Unit for volume in metric system is cubic meter. It is equal to a volume of a cube whose all sides measure 1m. This is equal to 1000L. For watering cans that contain several liters units used is decimeter cubed. 1dm^3 = 1L