Negative or neutral Clearly, the ball will be attracted if its charge is negative. However, even if the ball is neutral, the charges in the ball can be separated by induction (polarization), leading to a net attraction.
Yes! But very unlikely.Remember the bullets vertical velocity goes to zero before it starts to return to earth. If this is happening around the height of the plane the pilot could grab it. This would of course take lots of luck and extraordinary timing. But still physically possible.
It has more kinetic energy than the gunWhile it is true that the magnitudes of the momenta of the gun and the bullet are equal, the bullet is less massive and so it has a much higher velocity. Since KE is related to v2, the bullet has considerably more KE and therefore can do more damage on impact.
18 m/sThe initial momentum is zero, so the momenta of Amy and Gwen must be equal and opposite. Since p = mv, then if Amy has 3 times more mass, we see that Gwen must have 3 times more speed.
4 times the workThe elastic potential energy is 1/2 kx2. So in the second case, the elastic PE is 4 times greater than in the first case. Thus, the work required to stretch the spring is also 4 times greater.
Block on flat surfaceFor the flat surface, we know that N = W. For the incline, due to the angle of the incline, N < W. In fact, we can see that N = W cos(). Since Cos() can only be between 0 and 1 we know N must be less than W.