7TH GRADE · POWERS
Elasticity and resultant
Deformation, Hooke's law, dynamometer and addition of forces on one straight line.
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Basic Concepts
deformation
A change in the shape or size of a body under the influence of external forces is called deformation.
Elastic deformation disappears after the load is removed, while plastic deformation retains a noticeable residual trace.
Hooke's law
At low elastic deformation, the elastic force is proportional to the elongation of the body.
Stiffness shows how much force is needed for a unit elongation; beyond the elastic limit, the simple relationship breaks down.
Resultant force
One force that replaces the combined action of several forces and causes the same change in motion.
Co-directed forces add, and opposite forces subtract; the direction of the result coincides with the greater force.
Physical quantities
Elastic force
The force generated during deformation and directed toward restoring the shape.
Unit: newton ·
Elongation
Change in the length of an elastically deformed body.
Unit: meter ·
Hardness
The proportionality coefficient between elastic force and elongation.
Unit: newton per meter ·
Resultant
A force equivalent to the combined action of several forces.
Unit: newton ·
Lesson formulas
Hooke's law modulo
The modulus of the elastic force is equal to the stiffness multiplied by the elongation.
Condition: Only for small elastic deformation.
Co-directed forces
The resultant of codirectional forces is equal to the sum of their modules.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.