Two boys on skateboards are facing each other. they push off, the first boy (mass: 43.8 kg) traveling backward at 2.1 m/s. if the second boy is now traveling at 3.09 m/s, what is his mass?

The mass of the second boy is, m = 29.77 kg

Explanation:

Given data,

The mass of first boy, M = 43.8 kg

The velocity of first boy, V = -2.1 m/s

The velocity of second boy, v = 3.09 m/s

Then mass of second boy, m = ?

According to the law of conservation of momentum,

                                    mv + MV = 0

                                     m = - MV / v

Substituting the values,

                                     m = 43.8 x 2.1 / 3.09

                                      m = 29.77 kg

Hence, the mass of the second boy is, m = 29.77 kg

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 duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.