If you run 10 km east and then turn around and run 7 km west, how much total distance have you travelled? A. 17 km B. 70 km C. 3
2 answers:
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a. 25 joules of work is done by the object.
Explanation:
According to the work-energy theorem, the work done ON an object is equal to the change in kinetic energy of the object, therefore:
where
is the final kinetic energy of the car, with
m = 2 kg being the mass of the car
v = 0 is the final speed of the car (brought to rest)
is the initial kinetic energy of the car, with
u = 5 m/s being the initial speed of the car
Substituting numbers, we find:
The negative sign means that the work done ON the car is negative: this means therefore that the work has been actually done BY the car. In fact, the car has lost its kinetic energy: this means that it has done work on the surrounding, converting its kinetic energy into other forms of energy.
Learn more about work and kinetic energy:
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