Final answer:
No work is done when holding an object stationary (no displacement), when a force is perpendicular to displacement, or when an object moves at constant velocity (no net force in the direction of motion).
Step-by-step explanation:
common situations where no work is done.
In physics, work is defined as the product of the force applied to an object and the displacement of the object in the direction of the force. There are three common situations where no work is done:
- Vertical Hold: When holding an object still in a vertical position, such as holding a briefcase, no displacement occurs, therefore work is zero (W = 0).
- Perpendicular Force: When a force is applied perpendicular to the direction of displacement, such as pushing against a wall to no effect, there is no component of force in the direction of motion, so no work is done.
- Constant Velocity: If an object moves at constant velocity on a frictionless surface, no net force is required to maintain the velocity. If no additional force is applied in the direction of motion, no work is done.
Here are detailed examples explaining the situations:
- In everyday terms, if you hold a book above your head, you might feel like you are doing work due to muscle fatigue. However, in physics, since the book is not moving, no energy is transferred to the book, so no work is done.
- If someone pushes a wall with force, the wall does not move. The force is there, but because there is no displacement in the direction of that force, work is done equals zero.
- If you carry a briefcase while walking at a steady pace on flat ground, you are applying a force to hold it against gravity, but you are not doing work on the briefcase in the direction of your displacement, which is horizontal.