The forces acting on a plastic bucket containing water held above ground level are gravity (downward) and your hand’s upward force (muscular force or normal force). These forces are balanced, meaning they are equal in magnitude and opposite in direction, resulting in a net force of zero. This zero net force prevents the bucket from accelerating, keeping it stationary in your hand.
Elaboration:
Gravity:
Earth exerts a force on the bucket (and the water inside), pulling it downwards. This force is known as gravity.
Upward Force (Muscular/Normal):
Your hand exerts an equal and opposite force upwards, preventing the bucket from falling. This can be thought of as either a muscular force (from your hand muscles) or a normal force (the contact force between your hand and the bucket).
Balanced Forces:
Because these forces are equal and opposite, they cancel each other out, creating a net force of zero on the bucket.
No Change in Motion:
According to Newton’s first law of motion (inertia), an object at rest (like the bucket in your hand) will remain at rest unless acted upon by a net force. Since the net force is zero, the bucket remains stationary and doesn’t change its state of motion.