Ralph wants to move a 60.0\text{ kg}60.0 kg60, point, 0, start text, space, k, g, end text sofa. He applies a force of 480\text{ N}480 N480, start text, space, N, end text. Under these conditions, the sofa initially moves with an acceleration of 3.20\,\dfrac{\text{m}}{\text{s}^2}3 .20 s 2 m 3, point, 20, start fraction, start text, m, end text, divided by, start text, s, end text, squared, end fraction. Calculate the friction force on the sofa.

Which type of wave can travel without a medium

Askydiver weighing 140 lb (including equipment) falls vertically downward from an altitude of 19,000 ft and opens the parachute after 18 s of free fall. assume that the force of air resistance, which is directed opposite to the velocity, is of magnitude 0.55|v| when the parachute is closed and is of magnitude 14|v| when the parachute is open, where the velocity v is measured in ft/s. assume that acceleration due to gravity has magnitude 32 ft/s/s; remember that weight is the product of mass and gravitational acceleration. (a) find the speed of the skydiver when the parachute opens. (b) find the distance fallen before the parachute opens. (c) what is the limiting velocity vl after the parachute opens? (d) determine how long the sky diver is in the air after the parachute opens. (e) plot the graph of velocity versus time from the beginning of the fall until the skydiver reaches the ground.

Carbon is allowed to diffuse through a steel plate 15 mm thick. the concentrations of carbon at the two faces are 0.65 and 0.30 kg c/m^3 fe, which are maintained constant. if the preexponential and activation energy are 6.2 x 10-7 m2 /s and 80,000 j/mol, respectively, compute the temperature at which the diffusion flux is 1.43 x 10^-9 kg/m^2 -s.