# Homework Help: How to Calculate the forces when carrying a gurney

1. May 29, 2013

### Science4ver

1. The problem statement, all variables and given/known data

A Soccerplayer is injured and placed flat on 2 meter long gurney carried by two men.

The soccerplayer has weight of 81 kg and the gurney has a weight of 10 kg.

1) Calculate the force from the gurney onto the player's hand which is at position 0.8 meters from the left end of gurney and Calcuate the force from the gurney on the plays hip which is at position 1 meters on the gurney.

2) One of guys who carry the gurney with the gurney with the player on it can only carry 450 N. How long does the player have to move on gurney to for this guy being able to do his job?
its not mentioned how much other guy is able to carry.

2. Relevant equations

F = G * (m1 * m2)/r^2

3. The attempt at a solution

1) Do I use the equation F = G * (m1*m2)/r^2 to calculate the two forces.

2) Do I calcuate the center of mass?

2. May 30, 2013

### SteamKing

Staff Emeritus
The problem statement is not clear, but I am pretty certain that the force of gravitational attraction between the gurney and the soccer player is negligible compared to the gravitation attraction between the earth and the gurney and soccer player.

1. No.

2. Probably.

3. May 30, 2013

### Science4ver

The only other way I can come up with would to first calculate the force enacted on gurney

F_Gurney = m_gurney * g

then the forces enacted on the person

F = m_person * g

and if the person is placed at position
delta x = 0.8 m the the amount of Force enacted on the person at that position

F_total = F_Gurney + F_person * delta x?

If not how would you surgest I calculate this? Because no friction between the man and gurney is mentioned in the problem.

Best Regards Alfred

4. May 30, 2013

### haruspex

Is the question quoted accurately? It would make more sense as:
1) Calculate the force from the gurney on the player in the vicinity of the player's hand ...
Then, assuming the player's mass is uniformly distributed along the gurney, you can use moments to get an answer.

5. May 30, 2013

### Science4ver

Thanks for your answer, you version is what I meant. Its translated from a non english language :)

Which momentum formula do I use? Which takes position into account?

Cause I am only familar with

P=mv

Best regards
Alfred

6. May 30, 2013

### HallsofIvy

The force the gurney applies to the player's hand and leg is exactly the force the hand and leg apply to the gurney- their weight. And that is not given in the problem.

7. May 30, 2013

### Science4ver

Hello Hallsoftly and thank you for your answer. A previous poster mentioned this problem could solved by calculating the momentum at the hand and hip at their respective position? Because the acceleration look to me to be zero?

8. May 30, 2013

### haruspex

I wrote 'moment', not momentum. But it was nonsense anyway. If, as I suggested, you have to assume the player's weight is uniformly distributed then all you can calculate is the force per unit length - it doesn't make sense to ask what the 'force' is at a given point. And it will be the same at all points along the gurney.
Maybe the translation is still not quite right.