# Application of Newton's forces

1. Jun 7, 2009

### dREAPER

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

When a patient’s injured neck is healing, it is often desirable to prevent the weight of the head from pushing down on the neck. This can be accomplished with the system of pulleys shown in the figure. The pulleys are all small and extremely light in weight and have no appreciable friction. Typically, a person’s head makes up 7.00% of his or her body weight.

If the head of a 77.0 kg person is to be supported completely by the apparatus shown, what should the mass of W be? Start with a free-body diagram of the head.

I drew out a free body diagram, but don't know where to go from there.

2. Jun 7, 2009

### dx

Where is the figure?

3. Jun 7, 2009

### dREAPER

Last edited by a moderator: May 4, 2017
4. Jun 7, 2009

### dx

If the tension in the rope is T, what is the force exerted by the apparatus on the head?

5. Jun 7, 2009

### dREAPER

mg? With T pointing upward.

6. Jun 7, 2009

### dx

T points along the rope. There are four places where the tension exerts forces on the wheels. At two of these places, T points upward, and at the other two it points at an angle of 37 degrees to the vertical. You have to find the vertical componets of all these and add them up to find the total vertical force exerted on the head.