Two bicycle tires are set rolling with the same initial speed of 3.90 m/s along a long, straight road, and the distance each travels before its speed is reduced by half is measured. one tire is inflated to a pressure of 40 psi and goes a distance of 18.6 m ; the other is at 105 psi and goes a distance of 93.1 m . assume that the net horizontal force is due to rolling friction only and take the free-fall acceleration to be g = 9.80 m/s2 . what is the coefficient of rolling friction (uk) for the tire under low pressure?

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?