A person of mass 80 kg escapes from a burning building by jumping from a window situated 30 m above a catching net. The acceleration of gravity is 9.8 m/s2 . If air friction exerts a constant force of 100 N on her as she falls, determine her speed just before she hits the net:
1. 24.6495 m/s
2. 22.9396 m/s
3. 6.37868 m/s
4. 17.4299 m/s

Her speed just before she hits is 24.6495 m/s .

Explanation:

Given :

Mass of person , m = 80 kg .

Height from which it jumped , h = 30 m .

acceleration of gravity is , .

Force exerted by air friction , f = 100 N .

Now , force exerted by gravity is :

Therefore , net force experience by the body is :

Therefore , net acceleration of body is :

So by equation of motion :

So , her speed just before she hits is 24.6495 m/s .

Therefore , this is the required solution .

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.