The 70.0-kg climber in Fig. 4–72 is supported in the "chimney" by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between his back and the wall, are 0.80 and 0.60, respectively. What is the minimum normal force he must exert? Assume the walls are ver- tical and that the static friction forces are both at their maximum. Ignore his grip on the rope.

490 N

Explanation:

Please refer to the diagram below. Since the climber is currently at rest, we know that all forces must be equal.

∑F = 0

The normal forces, N, exerted on the climber in x-direction, and , are equal.

----------------------------------- Eq. ( 1 )

The forces exerted on the climber in y-direction are equal to zero.

We know that Friction F, is equal to μN, where μ  is the coefficient of friction.

    -------------------------------- Eq. ( 2 )

(m is the mass of the climber and g is gravity)

Substituting Eq. ( 1 ) in Eq. ( 2 )

Since from equation 1, we know that the normal force exerted is 490N.

i believe the answer would have to be a dependable person

a manufacturer of printed circuit boards uses exponential smoothing with trend to forecast monthly demand of its product. at the end of december, the company wishes to forecast sales for january. the estimate of trend through november has been 200 additional boards sold per month. average sales have been around 1000 units per month. the demand for december was 1100 units. the company uses α = 0.20 and β = 0.10. make a forecast including trend for the month of january.