To find the mass of the ball, we can use the formula for momentum:
Momentum = mass × velocity
Given that the momentum is 7 kg m/s and the velocity is 20 m/s, we can rearrange the formula to solve for mass:
mass = Momentum / velocity
Substituting the given values:
mass = 7 kg m/s / 20 m/s
mass = 0.35 kg
Therefore, the mass of the ball is 0.35 kg.