Mutual Interaction of Bodies

• If one thing acts on another, the other one acts back.

Mutual Interaction of Bodies

• The interaction of bodies is not one-sided.
• If body A acts on body B, then body B also acts on body A.

Results of the Mutual Interaction of Bodies

• Deformation of a body is a change in the shape of a body.
• Change in the state of motion of a body include:
  • Starting movement
  • Stopping movement
  • Changing the direction of movement
  • Changing the magnitude of the speed of the body

Ways Mutual Interaction Can Occur

• Mutual contact of bodies
• Through physical fields

Examples of physical fields

• Magnetic force interaction between a magnet and a ferromagnetic material through a magnetic field
• Gravitational force interaction between the Earth and its artificial satellite through a gravitational field
• Electric force interaction between a electrified ruler and pieces of paper through an electric field

Force as a Physical Quantity

• The vector of force includes vector line + arrow indicating direction
• 1 cm measure equals approximately 1 N
• The magnitude of the force vector is F = 6 N, |F| = 6 N
• The vector line and arrow indicate the direction of the vector.
• The length of the segment represents the magnitude of the vector.

Magnetic Force Increase

• As magnets get closer, the magnetic force with which they interact increases.

Measuring Force with a Force Meter (Silometer)

• A dynamometer that measures force
• Basic parts of a dynamometer: hook, spring, scale, casing
• The main part of the dynamometer is a spring, which extends under the action of the measured force.
• Spring extension in the dynamometer is directly proportional to the applied (measured) force.

Spring Stiffness

• Spring stiffness characterizes the dynamometer spring.
• Numerical value equals the force that extends the spring by 1 meter.
• F = k * Δl
  • k = F / Δl
  • [k] = N.m⁻¹

Isolated Body

• The mutual interaction is not observed if bodies are far enough apart.
• A body that is far enough away from all other bodies and is not acted upon by any field is called an isolated body.
• With an isolated material point, the dimensions of the body are ignored.

Examples of Isolated Bodies

• Gravitational force acting on a body placed on a pad or suspended is compensated by another force.
• All bodies in which the force action of other bodies is compensated behave like isolated bodies.

Test Questions and Answers

• Result of mutual interaction of bodies: change in shape of bodies or change in motion of bodies
• Interaction of bodies occurs- due to mutual contact of bodies
• Magnitude of mutual action of bodies described-by force
• Behavior of isolated bodes occurs- when force action of bodies is compensated