When an object performs work, it transfers some of its energy to another object or system. This action results in a change in the energy possessed by both the object doing the work and the object or system receiving the work.
Energy Transfer During Work Done by an Object
Based on the principles of physics, specifically the concept of energy transfer through work:
When work is done by a system or object, it gives some of its energy to something else. This means the object performing the work expends or transfers its own energy to exert a force over a distance on another object.
This process directly impacts the energy levels involved:
- The object doing the work loses some of its mechanical or internal energy.
- The object or system receiving the work gains energy (either mechanical, internal, or other forms).
Think of it like giving something away – you have less of it afterward. When an object does work, it "gives away" energy.
How Energy is Given Away
Work is the process by which energy is transferred when a force is applied over a distance. When an object does work, it applies a force that causes displacement in another object. This interaction facilitates the energy transfer.
For instance, the reference mentions: "Throwing a ball means a hand applies a force as an arm swings forward." In this scenario, the hand and arm (the system/object doing the work) apply force on the ball (the object receiving the work). As the arm moves the hand forward, the hand does work on the ball, transferring energy from the person's arm to the ball, causing it to accelerate and gain kinetic energy. This energy came from the person's body (chemical energy converted to mechanical energy in the muscles).
Examples of Work Done by an Object
Here are a few practical examples where an object or system does work:
- A compressed spring expands and pushes a block: The spring does work on the block, transferring its stored potential energy to the block as kinetic energy.
- A car engine moves the car: The engine (as part of the car system) does work against resistive forces like friction and air resistance, transferring energy from the fuel combustion to the car's motion.
- A person lifting a weight: The person's muscles do work on the weight, transferring chemical energy into the gravitational potential energy of the weight.
In each case, the object performing the work expends or transfers its energy to another object or system.
Work Done By vs. Work Done On
It's crucial to distinguish between work done by an object and work done on an object, as they represent opposite sides of the same energy transfer.
| Aspect | Work Done By an Object | Work Done On an Object |
|---|---|---|
| Energy Change | Object loses energy | Object gains energy |
| Direction | Force and displacement are typically in the direction the object is moving or acting upon something else | Force applied by an external agent is typically in the direction of the object's displacement |
| Perspective | Focusing on the object that is the source of the force/motion | Focusing on the object that is the recipient of the force/motion |
The reference highlights this distinction: "When work is done on a system or object, energy is added to it. When work is done by a system or object, it gives some of its energy to something else."
Key Takeaway
Ultimately, when work is done by an object, it serves as a mechanism for that object to transfer energy outwards, resulting in a decrease in its own energy and a corresponding increase in the energy of whatever it is acting upon. This principle is fundamental to understanding energy transformations in physics.
