The 78 kg climber here is supported in the "chimney" by the friction forces exerted on her shoes and back. the static coefficients of friction between her shoes and the wall, and between her back and the wall, are 0.88 and 0.63, respectively. what is the minimum normal force he must exert? assume the walls are vertical and that friction forces are both at a maximum.

If a rock is thrown upward on the planet mars with a velocity of 12 m/s, its height (in meters) after t seconds is given by h = 12t − 1.86t2. (a) find the velocity of the rock after two seconds. m/s (b) find the velocity of the rock when t = a. 12−3.72a m/s (c) when will the rock hit the surface? (round your answer to one decimal place.) t = s (d) with what velocity will the rock hit the surface? m/s