D; solar system, because the planets are inside it.
As the box is moving with a constant velocity, the two forces acting on the box are canceling each other.
Then friction force = 80 Newtons but in the opposite direction.
Friction force = Mu * Normal force exerted by ground = Mu * weight of box
So we find Mu.
Mu = coefficient of friction between box and horizontal surface
= Force of friction / weight = 80 / 50 * 9.81 = 0.163
When an identical box is placed on top, the force of friction is
= Mu * total weight = 0.163 * (50+50) * 9.81 = 159.9 Newtons
Answer: False
Explanation: The circulatory system of the body consists of the heart, blood vessels and blood. The deoxygenated blood from the body is carried to the heart.
Here, the deoxygentaed blood is converted into oxygenated by removing carbon dioxide from them and making it oxygenated.
The impure blood from the body is collected by the right ventricle and transported to the lungs for purification and then transported to the body.