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How do Work and Energy interact in vital life processes and Machine operations?
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Requirement of Life: Necessities for vital processes and Strenuous activities
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- All living beings require energy for their life processes and activities.
- Activities that are more strenuous necessitate more energy.
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Necessity for Life: Fueling vital activities for Survival and Mobility:
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- Similarly, animals also need energy for various activities such as running, jumping, or moving away from threats.
- Machines, on the other hand, often require fuel like petrol and diesel to operate.
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Work in Physics: From everyday perceptions to Scientific principles
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Work: Everyday vs Scientific Definitions
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- Common parlance treats any physical or mental labor as work.
- However, by the scientific definition, many activities we consider as “working hard” may involve little to no “work”.
- Example: Pushing a rock without it moving or holding a load without moving it does not qualify as work in science, even if they tire you out.
- Climbing stairs or a tree involves work because there is displacement against a force.
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Scientific Principles and Conditions
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- Pushing a pebble, pulling a trolley, and lifting a book are all examples where work is done in the scientific sense.
- Two conditions must be met for work to be recognized in science:
- A force should act on an object.
- The object must undergo displacement.
- If either condition is unmet, work hasn’t been done.
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Work Done by a Constant Force: Positive and Negative Forces in Physics:
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- Definition: In the realm of work and energy, the definition states that work is the product of force and the displacement in the direction of the force: W = F × s.
- Work has only magnitude, not direction.
- The unit of work is the newton-meter (N m) or joule (J).
- When force or displacement is zero, the work done is also zero.
- Positive Work: Work done is positive when force and displacement are in the same direction.
- Negative Work: Conversely, work is negative when the force acts opposite to the direction of displacement.
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Force and Work: Dynamic Interplay in Positive and Negative Directions
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Force and Displacement in the Same Direction:
- Example: A baby pulls a toy car parallel to the ground.
- The force exerted by the baby is in the direction of the car’s displacement. Here, the work done is calculated as the product of force and displacement.
- In such cases, the work done is taken as positive.
Force Opposite to the Direction of Displacement:
- Consider an object moving uniformly in one direction.
- A retarding force, denoted as F, acts opposite to its movement.
- The angle between the directions of the force and displacement is 180°.
- If the object stops after displacement ‘s’, the work done by force F is negative.
- It’s represented mathematically as either F × (–s) or (–F × s).
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