An object has a mass of $5 kg$ . The object's kinetic energy uniformly changes from $150 KJ$ to $42KJ$ over $t in [0,8s]$ . What is the average speed of the object?

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Answer 1 · 2016-11-12T07:17:17

The average speed is $=142.5 ms^(-1)$

The kinetic energy $=(mv^2)/2$
Let $u_0$ be the initial velocity and
$u_1$ the final velocity.
The average speed is $=(u_0+u_1)/2$

$m*u_0^2/2=150*10^3$
$:. u_0^2=150*10^3/5$ $=>$ $u_0=sqrt(30*10^3)=173.2 ms^(-1)$

$m*u_1^2/2=42*10^3$
$:. u_1^2=42*10^3/5$ $=>$ $u_1=sqrt(42*200)=91.7 ms^(-1)$

The average speed is $(173.2+91.7)/2=142.5 ms^(-1)$

An object has a mass of 5 kg5 kg. The object's kinetic energy uniformly changes from 150 KJ150 KJ to 42KJ 42KJ over t in [0,8s]t in [0,8s]. What is the average speed of the object?