# If an object with a mass of 12 kg  changes speed from 3 m/s to 1m/s, by how much does its kinetic energy change?

##### 1 Answer

decrease by $48 \setminus J$

#### Explanation:

Change in kinetic energy of an object of mass $m = 12$ kg due to change in speed from ${v}_{1} = 3 \frac{m}{s}$ to ${v}_{2} = 1 \frac{m}{s}$

$= \frac{1}{2} m {v}_{2}^{2} - \frac{1}{2} m {v}_{1}^{2}$

$= \frac{1}{2} \left(12\right) {3}^{2} - \frac{1}{2} \left(12\right) {1}^{2}$

$= - 48 \setminus J$

The above negative value shows that the kinetic energy of object decrease by $48 \setminus J$