7TH GRADE · WORK, POWER AND ENERGY
Mechanical work and power
When work is done and how the speed of its completion is compared.
The entire theory of the lesson is collected here; you can read it without an account. In interactive mode, the same theory appears as cards, followed by questions. with checking the answer and task, and progress is saved.
Basic Concepts
Mechanical work
A force does mechanical work when a body moves and the force has a component along the displacement.
For a constant force along the motion, the work is equal to the product of the force and the path; without movement, mechanical work is zero.
Power
A physical quantity equal to work performed per unit of time and characterizing the speed of work.
Two mechanisms can do the same work, but the more powerful one will do it in less time.
Conditions of work
Work is positive if the force is directed towards the movement and negative if the force is directed against the movement.
At the linear motion level, it is important to first check for the presence of displacement and the relative direction of force and motion.
Physical quantities
Mechanical work
Energy transferred by the action of a force when a body moves.
Unit: joule ·
Power
Work done per unit of time.
Unit: watt ·
Moving along the force
The distance traveled by a body in the direction of a constant force.
Unit: meter ·
Opening hours
Duration of mechanical work.
Unit: second ·
Lesson formulas
Constant force work
When the directions coincide, the force transfers energy equal to the product of force and displacement.
Power
Power is equal to the work done divided by the time it takes to complete it.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.