A1200 kg car is practicing on a flat test track. the car begins moving in a 100 m radius circle at a speed of 20 m/s. viewed above, it is traveling around the circle clockwise, beginning from the top of the circle.(a) what is the centripetal acceleration of the car? (b) how much force is required for this? (c) what is the coefficient of friction between the tires and the track? three quarters of the way around the track the car hits a 4m patch of oil, which reduces friction of the tires to zero.(d) which way does the car move, with what acceleration? the driver now applies the brakes, aiming the car straight ahead.(e) if the force stopping the car is the same as your answer from part (c), how much time does it take to stop the car.

The cerebellum controls? thirst sensations sleep-wake cycles hand-eye coordination heart rate and pulse

Some material consisting of a collection of microscopic objects is kept at a high temperature. a photon detector capable of detecting photon energies from infrared through ultraviolet observes photons emitted with energies of 0.3 ev, 0.5 ev, 0.8 ev, 2.0ev, 2.5ev, and 2.8ev. these are the only photon energies observed. (a) draw and label a possible energy-level diagram for one of the microscopic objects, which has four bound states. on the diagram, indicate the transitions corresponding to the emitted photons. explain briefly. (b) would a spring–mass model be a good model for these microscopic objects? why or why not? (c) the material is now cooled down to a very low temperature, and the photon detector stops detecting photon emissions. next, a beam of light with a continuous range of energies from infrared through ultraviolet shines on the material, and the photon detector observes the beam of light after it passes through the material. what photon energies in this beam of light are observed to be significantly reduced in intensity (“dark absorption lines”)? explain briefly.

The radioactive isotope of lead, pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.3 hours. if 1 gram of this isotope is present initially, how long will it take for 80% of the lead to decay? (round your answer to two decimal places.)