Question

1. identify the forces

situation
balanced or unbalanced?
a book resting on a desk
a ball rolling and slowing
down
a person pushing a box
and it starts moving
a car moving at the same
speed in a straight line

Explanation:

• For a book resting on a desk: The book is at rest. According to Newton's first law, when an object is at rest, the forces acting on it (gravity pulling it down and the normal force from the desk pushing it up) are balanced.
• For a ball rolling and slowing down: The ball's speed is changing. A change in speed (acceleration) implies an unbalanced force (friction acting against its motion).
• For a person pushing a box and it starts moving: The box starts moving from rest. A change in motion (from rest to motion) means there is an unbalanced force (the applied push force overcoming static friction).
• For a car moving at the same speed in a straight line: The car has a constant velocity. When velocity is constant (no acceleration), the forces acting on it (e.g., thrust force and air - resistance/friction force) are balanced.

Answer:

• A book resting on a desk: Balanced
• A ball rolling and slowing down: Unbalanced
• A person pushing a box and it starts moving: Unbalanced
• A car moving at the same speed in a straight line: Balanced