A person pulls a 50. kg box pictured below with a force of 100. N.  The coefficient of kinetic friction is 0.15.  How much of the force acts in the direction of motion?How much energy is transferred (via working) by the person who pulls the box a distance of 10. m?
Is the box moving at constant speed? Explain how you know. What does this tell you about the kinetic energy Ek of the system?
How much energy is stored as internal energy due to friction in the pulling process over the 10.m?
What eventually happens to this energy?

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)

When a vertical beam of light passes through a transparent medium, the rate at which its intensity i decreases is proportional to i(t), where t represents the thickness of the medium (in feet). in clear seawater, the intensity 3 feet below the surface is 25% of the initial intensity i0 of the incident beam. what is the intensity of the beam "10" feet below the surface? (give your answer in terms of i0. round any constants or coefficients to five decimal places.)

Which component of the earth’s atmosphere is decreased due to photosynthesis?