# physics

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Your physics teacher drives an ideal frictionless car of mass 1000 kg which coasts along the level road to his home at a constant speed of 48 km/h with the engine turned off. It then coasts 40 m up his sloping driveway and comes to rest at the top without any braking required. One day he found that his engine had to develop 30 kilowatts of power to maintain a steady speed of 48 km/h on the level road due to a layer of loose snow on the road. He quickly calculated the new speed required to for him to coast up his driveway with the engine switched off as usual. He assumed that the snow on the hill would give the same constant retarding force as the snow on the level. What was the new speed?

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