Determine the force in members DC, HC, and HI of the truss and state if the members are in tension or compression. 50kN 40 kN -2 m -2 m D F H 1.5 m -30 kN 15 m B40 kN 1.5 m

A carbon nanotube is a nanometer-scale cylindrical tube composed of carbon atoms. One of its interesting properties is a very large Youngs modulus, measured to be more than 1.000 1012 N/m2. A tensile stress of 5.3 1010 N/m2 is exerted on a particular nanotube with a Youngs modulus measured at 2.130 1012 N/m2. Assuming the nanotube obeys Hookes law, by what percentage does the atomic spacing increase?

An object is being weighed using an unequal-arm balance (Fig. P14.76). When the object is in the left pan, a downward force of 3.0 N must be exerted on the right pan to balance the gravitational force on the object. When the object is in the right pan, a downward force of 2.0 N must be exerted on the left pan to balance the gravitational force on the object. Determine the magnitude of the gravitational force on the object. FIGURE P14.76

The inner planets of our solar system are represented on a mobile constructed from drinking straws and light strings for aschool project (Fig. P14.22). The mass of the piece representingthe Earth is 25.0 g, and the mass of the straws can be ignored.(The lengths shown are not proportional to actual distances inthe solar system.) What is the mass of the piece representinga. Mars, b. Venus, and c. Mercury? FIGURE P14.22

Explain why knowledge of E(x, y, z) is not sufficient to determine V(x,y,z). What about the other way around?

Review. Assume a certain liquid, with density 1 230 kg/m3, exerts no friction force on spherical objects. A ball of mass 2.10 kg and radius 9.00 cm is dropped from rest into a deep tank of this liquid from a height of 3.30 m above the surface. (a) Find the speed at which the hall enters the liquid. (b) Evaluate the magnitudes of the two forces that are exerted on the ball as it moves through the liquid. (c) Explain why the ball moves down only a limited distance into the liquid and calculate this distance. (d) With what speed will the ball pop up out of the liquid? (c) How does the time interval tdown, during which the ball moves from the surface down to its lowest point, compare with the lime interval tup for the return trip between the same two points? (f) What If? Now modify the model to suppose the liquid exerts a small friction force on the ball, opposite in direction to its motion. In this case, how do the time intervals tdown and tup compare? Explain your answer with a conceptual argument rather than a numerical calculation.

Review. A student is supplied with a stack of copy paper, ruler, compass, scissors, and a sensitive balance. He cuts out various shapes in various sizes, calculates their areas, measures their masses, and prepares the graph of Figure PI.51. (a) Consider the fourth experimental point from the top. How far is it from the best-lit straight line? Express your answer as a difference in vertical-axis coordinate, (b) Express your answer as a percentage, (c) Calculate the slope of the line, (d) State what the graph demonstrates, referring to the shape of the graph and the results of parts (b) and (c). (e) Describe whether this result should be expected theoretically, (f) Describe the physical meaning of the slope.

Show that the Reynolds number NRis unitless by substituting units for all the quantities in its definition and cancelling.

When a circus performer performing on the rings executes the iron cross, he maintains the position at rest shown in Figure P12.37a. In this maneuver, the gymnasts feet (not shown) are off the floor. The primary muscles involved in supporting this position are the latissimus dorsi (lats) and the pectoralis major (pecs). One of the rings exerts an upward force Fk on a hand as show n in Figure P12.37b. The force Fs, is exerted by the shoulder joint on the arm. The latissimus dorsi and pectoralis major muscles exert a total force Fm on the arm. (a) Using the information in the figure, find the magnitude of the force Fm for an athlete of weight 750 N. (b) Suppose a performer in training cannot perform the iron cross but can hold a position similar to the figure in which the arms make a 45 angle with the horizontal rather than being horizontal. Why is this position easier for the performer? Figure P12.37

You have scored a great internship with NASA, working on planning for an upcoming mission to Mars. The transfer orbit to Mars will last for several months and will require reclamation of the oxygen in the carbon dioxide exhaled by the crew. In one method of reclamation, 1.00 mol of carbon dioxide produces 1.00 mol of oxygen and 1.00 mol of methane as a byproduct. The methane is stored in a tank under pressure and is available to control the orientation of the spacecraft by controlled venting. A single astronaut exhales 1.09 kg of carbon dioxide each day. If the methane generated in the respiration recycling of three astronauts during one week of flight is stored in an originally empty 150-L tank at 45.0C, what is the final pressure in the tank?