A21.0 kg shopping cart is moving with a velocity of 4.0 m/s. it strikes a 9.0 kg box that is initially at rest. they stick together and continue moving at a new velocity. assume that friction is negligible. what was the momentum of the shopping cart before the collision? 0 kg⋅m/s 36 kg⋅m/s 168 kg⋅m/s 84.0 kg⋅m/s what was the momentum of the box before the collision? 168 kg⋅m/s 84.0 kg⋅m/s 0 kg⋅m/s 36 kg⋅m/s what is the velocity of the combined shopping cart–box wreckage after the collision? 9.3 m/s 4.0 m/s 2.8 m/s 0 m/s

Certain bacteria (such as aquaspirillum magnetotacticum) tend to swim toward the earth’s geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. if a transmission line carrying 100 a is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (assume that a field less than 5% of the earth’s field would have little effect on the bacteria. take the earth’s field to be 5.0 * 10-5 t, and ignore the effects of the seawater.)