Sara runs several times a week and always keeps track of how much time she runs each time she goes out. one day she forgets to take her stopwatch with her and wonders if she can still have some idea of her running time. as she passes a particular pond, she remembers that it is 5.6 km from her house. she knows from her previous training that she has a consistent pace of 3.4 m/s. how long has sara been running when she reaches the pond? a. 16 minutes c. 27.5 minutes b. 27.5 s d. 1 hour

The ultracentrifuge is an important tool for separating and analyzing proteins. because of the enormous centripetal accelerations, the centrifuge must be carefully balanced, with each sample matched by a sample of identical mass on the opposite side. any difference in the masses of opposing samples creates a net force on the shaft of the rotor, potentially leading to a catastrophic failure of the apparatus. suppose a scientist makes a slight error in sample preparation and one sample has a mass 10 mg larger than the opposing sample. if the samples are 12 cm from the axis of the rotor and the ultracentrifuge spins at 70,000 rpm, what is the magnitude of the net force on the rotor due to the unbalanced samples? ( be thorough on your answer)