Electromagnetic Waves
1. Gamma-ray bursters are objects in the universe that emit pulses of
gamma rays with high energies. The frequency of the most energetic
bursts has been measured at around 3.0 x 102 Hz. What is the wave-
length of these gamma rays?

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.

it has to be b, about 97 percent.

there are no contact forces mentioned on the list of choices that you've provided.