One side of a plant shelf is supported by a bracket mounted on a vertical wall by a single screw as shown in Figure P12.50. Ignore the weight of the bracket. (a) Find the horizontal component of the force that the screw exerts on the bracket when an 80.0 $\mathrm{N}$ vertical force is applied as shown. (b) As your grandfather waters his geraniums, the $80.0-\mathrm{N}$ load force is increasing at the rate 0.150 $\mathrm{N} / \mathrm{s}$ . At what rate is the force exerted by the screw changing? Suggestions: Imagine that the bracket is slightly loose. You can do parts (a) and (b) most efficiently if you call the load force $W$ and solve symbolically for the screw force $F .$