The fulcrum of a uniform 20-kg seesaw that is 4.0 m long is located 2.5 m from one end. A 30-kg child sits on the long end. Part A Determine the mass a person at the other end would have to be in order to balance the seesaw. Express your answer to two significant figures and include the appropriate units. m = nothing nothing

57 kg

Explanation:

Mass of seesaw = 20 kg

Length of seesaw = 4 m

Mass of child on the longer end = 30 kg

The weight of the seesaw acts at the center i.e. 2m

The algebraic sum of moments of all forces about any point is zero, hence, using the fulcrum as the reference point:

[x * 9.8* 1.5] - [20 * 9.8* (2.5 - 2)] - [30 * 9.8 * 2.5] = 0

=> 14.7x = (20*9.8*0.5) + 735

14.7x = 98 + 735

14.7x = 833

=> x = 833/14.7

x = 57 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.