8. Name the forces acting on a plastic bucket containing water held above
ground level in your hand. Discuss why the forces acting on the bucket do
not bring a change in its state of motion.
Answers
Answer:gravity
gravitational force
The forces acting on a stationary bucket held at a certain height from ground by a person are:
(i) gravitational force due to earth i.e. its weight
(ii) muscular force by the person
(iii) fluid force, by the water it contains, on its walls
These forces do not bring about any change in its state of motion because they all act at such conditions and directions that they maintain an equilibrium, i.e. the sum of forces becomes zero.
The muscular force applied by the person to hold and keep the bucket stationary has to be equal to the weight of it, i.e. the gravitational force on it due to earth. And the muscular force acts in upward direction, while the gravitational force acts on downward direction. Both being equal.in magnitude and opposite in direction, cancel out each other, showing the net force equal to Zero.
Similarly, we know that fluid in a container spread evenly in it. So, as stagnant (stationary) water is spread evenly in the bucket, it applies the same amount of force at every point on the wall of the bucket. The amount of force it exerts on the left wall is just the equal amount as it exerts on the right wall. Same with front and the back wall. Or the diagonally opposite walls. So, these fluid forces again cancel out each other, hence bringing about equilibrium in the bucker and no change in its state of motion.
As the fluid forces have balanced each other and so have the muscular and the gravitational forces acting on the bucket, the net force exerted on the bucket is also balanced i.e. equal to zero. As we know, that Force is solely a cause of motion, we also see that as there's ultimately an equilibrium/balanced force acting on the bucket, there is hence no change seen in its state of motion.