The kinetic energy (KE) can be calculated using the formula:
\[ KE = \frac{1}{2} mv^2 \]
where:
- \( KE \) is the kinetic energy,
- \( m \) is the mass,
- \( v \) is the velocity.
Given:
- \( KE = 3000 , J \)
- \( v = 10 , m/s \)
We can rearrange the formula to solve for mass \( m \):
\[ m = \frac{2 \cdot KE}{v^2} \]
Now, plug in the values:
\[ m = \frac{2 \cdot 3000 , J}{(10 , m/s)^2} \]
\[ m = \frac{6000 , J}{100 , m^2/s^2} \]
\[ m = 60 , kg \]
Therefore, the mass is 60 kg.
The correct answer is 60 kg.