10TH GRADE · DYNAMICS
Strength and Balance
Gravity, elasticity, friction, inclined plane and moment of force.
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
Universal gravity
Mutual attraction of any bodies with mass.
The attraction is mutual: bodies act on each other with forces equal in magnitude, and the force quickly decreases with distance.
Elastic force
The force that arises during deformation and is aimed at restoring the original shape of the body.
It counteracts deformation. For small tensions and compressions, its modulus is usually found using Hooke's law.
Friction force
A force that resists the relative motion of contacting surfaces.
Friction is directed along the surface and interferes with relative sliding or its initiation; its value depends on the state of the contact.
Mechanical balance
A condition in which a body does not receive translational and rotational acceleration.
For balance, a zero sum of forces and a zero total moment are simultaneously required. In this case, the body can be at rest or move uniformly.
Physical quantities
Gravitational constant
Coefficient in the law of universal gravitation.
Unit: newton square meter per square kilogram ·
Planet mass
The mass of a celestial body creating a gravitational field.
Unit: kilogram ·
Mass of the first body
Mass of the first interacting body.
Unit: kilogram ·
Mass of the second body
Mass of the second interacting body.
Unit: kilogram ·
Distance between bodies
The distance between the centers of interacting bodies.
Unit: meter ·
Spring stiffness
Spring deformation resistance coefficient.
Unit: newton per meter ·
Elongation
Change in the length of a deformed body.
Unit: meter ·
Ground reaction force
The force of support on the body.
Unit: newton ·
Body weight
The force exerted by a body on a support or suspension.
Unit: newton ·
Friction force
A force that resists the relative motion of surfaces.
Unit: newton ·
Friction coefficient
Dimensionless characteristic of friction of a pair of surfaces.
Unit: dimensionless quantity
Tilt angle
The angle of the inclined plane to the horizon.
Unit: radian ·
Longitudinal component of gravity
Component of gravity along an inclined plane.
Unit: newton ·
moment of force
Rotational action of a force relative to an axis.
Unit: newton meter ·
Shoulder of power
The shortest distance from the axis to the line of action of the force.
Unit: meter ·
Lesson formulas
Law of Gravity
The force of attraction is proportional to the product of masses and inversely proportional to the square of the distance.
Hooke's law
The elastic force is proportional to the deformation modulus.
Weight on horizontal support
In the absence of vertical acceleration, the weight is equal to the ground reaction force.
Sliding friction force
The friction force is equal to the coefficient of friction multiplied by the reaction of the support.
Friction on a horizontal surface
On a horizontal surface without vertical acceleration, the reaction of the support is equal to the force of gravity.
Component of gravity along the inclined
The longitudinal component of gravity is directed along the inclined plane.
Inclined support reaction
The normal reaction is equal to the perpendicular component of gravity.
Friction on an inclined plane
The frictional force on an inclined plane takes into account the reduced reaction of the support.
Acceleration near the surface of the planet
The acceleration of gravity is determined by the mass and radius of the planet.
The value of the gravitational constant
The gravitational constant sets the scale of gravitational interaction.
Translational equilibrium condition
The vector sum of forces in translational equilibrium is zero.
Rotational equilibrium condition
The algebraic sum of the moments of forces in rotational equilibrium is equal to zero.
moment of force
The moment of force is equal to the product of force and its arm.
Unit of moment of force
The moment of force is measured in newton meters.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.