Final answer:
After applying the kinetic energy formula and solving for mass, the result of approximately 13.15 kg does not match any of the options provided. This suggests an error either in the calculations or in the provided answer choices.
Step-by-step explanation:
To find the mass of the child based on the given kinetic energy and velocity, we use the kinetic energy formula:
KE = ½ mv²
Where KE is kinetic energy, m is the mass, and v is the velocity. We can rearrange the formula to solve for the mass:
m = ½ KE/v²
Plugging in the provided values:
m = ½ (400 J) / (3.9 m/s)²
We do the calculation:
m = 200 / 15.21
m ≈ 13.15 kg
This result does not match any of the provided options (A-D), indicating either a miscalculation or a mismatch in the provided choices. Assuming the kinetic energy and velocity are correct, none of the choices provided would be the mass of the child.