6. A balloon inflated with helium is able to float toward the ceiling because a) the weight of the balloon is greater than the weight of the air displaced by the balloon.
b) the density of the balloon is less than the density of the atmosphere.
c) The kinetic energy inside the balloon is less than the kinetic energy of the atmosphere
d) the pressure of the gas inside the balloon is greater than the atmospheric pressure.

b) the density of the balloon is less than the density of the atmosphere.

Explanation:

We must take into account that density is defined as the relationship between mass and volume.

The helium density is 0,1785 [kg/m3]

The air density is 1.2 [kg/m3]

Therefore a substance with lower density (helium) will try to rise on substances with heavier density (air).

An example of this is when we mix water with oil, the water is heavier than the oil, that is, the density of the water is greater than the density of the oil, therefore the oil will be located on the surface of the water and not at the bottom.

Another example is that of a balloon inflated with air is common, this balloon doesn't rise because the air density outside the balloon equals the air density inside the balloon, the balloon will fall to the ground since it contains the weight of the air contains the weight of the material of the balloon.

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.