Describe a physical situation in which a force is doing positive work on an object. How about a situation where a force is doing negative work? Zero work? Give examples of all three scenarios.
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A force that increase the internal energy of an object produces positive work, like lifting a box to a higher elevation or speeding up a car.
A force that decreases the internal energy produces negative work, like friction that slows an object in motion down.
A force that does not change the energy of an object produces 0 work. A centripetal force acting on object going around a corner will change the direction of motion, but may not change the kinetic energy, like a car enters a corner going 30 mph, turns 90 deg, and exits the corner going 30 mph. In that situation, the kinetic energy is the same.
A force that decreases the internal energy produces negative work, like friction that slows an object in motion down.
A force that does not change the energy of an object produces 0 work. A centripetal force acting on object going around a corner will change the direction of motion, but may not change the kinetic energy, like a car enters a corner going 30 mph, turns 90 deg, and exits the corner going 30 mph. In that situation, the kinetic energy is the same.