Man in Elevator: What is the Force Exerted on the Elevator Floor?

[Cole07]

Force Of Man On Elevator

Homework Statement

An 65- kg man stands in an elevator. What force does he exert on the floor of the elevator under the following conditions? The elevator is stationary.
Answer:637.65N

The elevator accelerates upward at 2.3 m/s2.
Answer:787.15N

The elevator rises with constant velocity of 3.1 m/s.

While going up, the elevator accelerates downward at 1.7 m/s2.
Answer:527.15N

The elevator goes down with constant velocity of 6.3 m/s.

Homework Equations

EF=0

The Attempt at a Solution

so far i have the ones where i allready have the acceleration but i don'tknow how to do the ones with velocity because i don't have a t(time) i thought maybe i could do the same and multiply 3.1m/s*65kg which is 201.5 and then use the formula EF=0 so EF=0=-201.5-637.65 which equals 839.15 but this was wrong, could you just give me an idea on how to get started and help would be greatly appreciated.

 

[Cole07]

Do I not have enough work swown?

 

[PhanthomJay]

Do I not have enough work swown?

you need only to look at Newton's first law to arrive at a solution. What is the acceleration of the elevator and person when they are moving at constant speed?

 

[Cole07]

how do i get to the acceleration when i don't have anything but weight and velocity?

 

[Cole07]

i have figured it out thank you for your help.