4. What is the momentum of a 78.0 N bowling ball with a velocity of 8.00 m/s?

Momentum = (mass) x (speed)

We don't know the mass of the bowling ball, but we know how much it weighs.  So if we knew the acceleration of gravity in the place where the ball is, we could calculate its mass.  The question doesn't tell us what planet the bowling ball is on.  So if we only use the information given in the question, there's no way to find the answer, and we're stuck here.

But I urgently need the points, so I'm going to go out on a limb here and make a big assumption:  I'll assume that the alley where this ball is rolling and bowling is located on planet Earth, where the acceleration  of gravity is around  9.8 m/s²  everywhere on the planet's surface.  NOW I can go ahead and answer the question that I just invented.

weight = m  g

Mass = (weight) / (g)

Mass = (78.0 N) / (9.8 m/s²)

Mass = 7.96 kilograms

Momentum = (mass) x (speed)

Momentum = (7.96 kg) x (8.00 m/s)

Momentum = 63.7 kg-m/s