A skydiver weighing 120kg drops vertically from a jet flying at 4.000m. Assume the force due to air resistance to be proportional to the velocity of the skydiver, with the proportionality constant b1= 20 N⋅sec/m before the cute is opened, and b2= 100 N⋅sec/m after the chute is opened. If the skydiver opens the chute after 60 seconds of free fall, find:  a. The total amount of time elapsed between dropping out of the plane and landing.  b. The velocity of the skydiver at the instant of landing on the ground.

A student presses a book between his hands, as the drawing indicates. The forces that he exerts on the front and back covers of the book are perpendicular to the book and are horizontal. The book weighs  25.8 N. The coefficient of static friction between his hands and the book is  0.326. To keep the book from falling, what is the magnitude of the minimum pressing force that each hand must exert?

The outside dimensions of a rectangular box (bottom and four sides, no top), made of aluminum, are 24 by 12 by 4 inches as shown in Figure 1. The wall thickness of the bottom and the sides is x in. W V == Y 4 in 12 in 24 in Figure 1 Rectangular aluminum box Given that the specific weight of aluminum is 0.101 kg/in³ and the volume of the aluminum V is calculated from the weight of the box, W by: Where y is the specific weight. (note: the weight of the box is 15 kg) a) Derive an expression that relates the weight of the box and the wall thickness, x. b) Use bisection method to find the root of the function in (a) accurate to within ε = 0.001, given that x = 0 and x = 0.4.