An object has a mass of $6 kg$ . The object's kinetic energy uniformly changes from $120 KJ$ to $72 KJ$ over $t in [0, 4 s]$ . What is the average speed of the object?

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Answer 1 · 2017-01-28T15:31:37

Average speed is $177.46$ $m/s$ .

As one Joule is equal to $1$ $kgm^2/s^2$ and as such the object's kinetic energy changes from $120,000KJ$ to $72000KJ$ .

As kinetic energy $KE$ is given by $1/2mv^2$ , velocity is given by $sqrt((2KE)/m)$

and initial velocity is $sqrt((2xx120000)/6)=sqrt40000=200$ $m/s$

and final velocity is $sqrt((2xx72000)/6)=sqrt24000=154.92$ $m/s$

and average speed is $(200+154.92)/2=354.92/2=177.46$ $m/s$ .

An object has a mass of 6 kg6 kg. The object's kinetic energy uniformly changes from 120 KJ120 KJ to 72 KJ 72 KJ over t in [0, 4 s]t in [0, 4 s]. What is the average speed of the object?