Q16. As long as the rope is massless, the force team A exerts on the rope is always equal and opposite the force team B exerts on the rope. The winner, however, is decided by motion with respect to the ground. If you make a free body diagram of both teams and the rope taken together, there are only two horizontal force components. These are the forces the ground exerts against the feet of the team members. The ground exerts a frictional force against the feet of team A which is the reaction to the force the feet exert against the ground. The same is true for team B. These forces exerted by the ground are in opposite directions. Whichever team has the greatest force exerted against its feet by the ground wins the contest and this is determined by how hard the team is able to push against the ground. How hard you are able to push against the ground depends on your own muscles, and the coefficient of static friction between the bottom of your feet and the ground. If the ground doesn't exert a frictional force against your feet to keep them from slipping, you cannot exert a large force against the ground.
Q5. The water in the pail tends to go in a straight line due to its velocity and any downward force tends to change this direction of motion. If the water is moving very fast, the force of gravity acting on the water and the force exerted by the bottom of the pail on the water will both be required to cause the water to follow the same circular path as the pail. As the water slows down, less centripetal force is required to make the water follow a circular path and the bottom of the pail exerts a smaller normal force on the water. Once the normal force exerted by the pail on the water reaches zero, the water starts to fall away from the bottom of the pail at the top of the path. At this and lower speeds, the weight of the water exerts more force than is required to force the water to follow the circular path of the pail and the water will eventually leave the pail when the speed is low enough.
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