Final answer:
The mass of the object can be found using the kinetic energy formula, and it calculates to 0.6349 kg, which does not match any of the given options; hence, there might be an error in the provided choices or the question.
Step-by-step explanation:
The question is asking to calculate the mass of an object given its speed and kinetic energy. The kinetic energy of an object is given by the formula KE = 0.5 × m × v², where KE is kinetic energy, m is mass, and v is velocity. Therefore, to find the mass m, we can rearrange the formula to m = 2 × KE / v².
Given:
KE = 140 J (Kinetic Energy)
v = 21 m/s (velocity)
Using the formula:
m = 2 × 140 J / (21 m/s)²
m = 280 J / 441 m²/s²
m = 0.6349 kg
However, none of the options (A) 3 kg, (B) 4 kg, (C) 5 kg, or (D) 6 kg are correct. It seems there might be a mistake in the given options or in the question itself as the calculated mass does not match any of the provided choices.