Final answer:
The kinetic energy of a 7 kg ball rolling at a velocity of 4 m/s is calculated using the formula KE = 1/2mv², which gives us 56 Joules. So, the correct answer is B) 56 J.
Step-by-step explanation:
To calculate the kinetic energy of a 7 kg ball rolling at a velocity of 4 m/s, we use the formula for kinetic energy, KE = 1/2mv², where m is mass and v is velocity. Plugging in the values, we get KE = 0.5 × 7 kg × (4 m/s)².
Carrying out the calculation: KE = 0.5 × 7 kg × 16 m²/s² = 56 J. Therefore, the correct answer is B) 56 J.