An example of balanced forces is a. a person skating back and forth on an ice rink. b. a tire with treads gaining speed on an icy road. c. two soccer players running in opposite directions. d. a book resting on a desk.
The correct answer and explanation is:
The correct answer is: d. a book resting on a desk.
Explanation (300 words):
Balanced forces occur when the forces acting on an object are equal in magnitude but opposite in direction, resulting in no change in the object’s motion. In simpler terms, the object either stays at rest or continues moving at a constant speed in a straight line. There is no acceleration when forces are balanced.
Let’s analyze the correct option:
A book resting on a desk is a classic example of balanced forces. The book experiences two main forces: gravity pulling it downward (its weight) and the normal force exerted by the desk pushing it upward. These two forces are equal in magnitude and opposite in direction. Because they cancel each other out, the net force on the book is zero, and the book remains stationary. Since there is no movement or change in motion, the forces are balanced.
Now let’s briefly consider why the other options are incorrect:
- a. A person skating back and forth on an ice rink involves motion, including changes in direction and possibly speed. That indicates unbalanced forces acting at various moments (such as friction or pushes).
- b. A tire with treads gaining speed on an icy road involves acceleration (gaining speed), which clearly indicates unbalanced forces. The force propelling the car forward is greater than the opposing friction or air resistance.
- c. Two soccer players running in opposite directions involves individual motion, and although they are running in opposite directions, they are not applying balanced forces on a single object. Each player is under different influences and is accelerating, which again implies unbalanced forces.
In conclusion, “a book resting on a desk” is the only scenario among the choices where the forces are equal and opposite, producing no movement or change in motion—making it the best example of balanced forces.