A ball hits a horizontal spring. As the spring is compressed, the ball comes to a stop. Then the spring pushes the ball back in the direction it came. Which one of the following describes the momentum of the system? *

The momentum of the system is larger after the collision with the spring.

The momentum of the system is smaller after the collision with the spring.

The momentum of the system is conserved before and after the collision with the spring, but not during the collision.

The momentum of the system is conserved before, during, and after the collision with the spring.

The base of a 50-meter tower is at the origin; the base of a 50-meter tree is at (0, 50, 0). the ground is flat and the z-axis points upward. the following parametric equations describe the motion of six projectiles each launched at time t = 0 in seconds. (i) r (t) = (50 + t2)k (ii) r (t) = 2t2 j + 2t2k (iii) r (t) = 50 i + 50 j + (50 − t2)k (iv) r (t) = 2t j + (50 − t2)k (v) r (t) = (50 − 2t) i + 2t j + (50 − t)k (vi) r (t) = t i + t j + tk (a) which projectile is launched from the top of the tower and goes downward? at time t = , the projectile hits the ground at point (x, y, z) = . (b) which projectile hits the top of the tree?