Physic Labs

Newtonian mechanics

Uniform linear motion

Observe uniform linear motion and its linear x–t graph. Verify x=x0+vtx = x_0 + vt, s=∣v∣ts = |v|t: the slope of the position graph gives the velocity.

Middle school

Equipment

  • 3D model of a point moving on a straight line with a trail
  • Time slider to sweep through the motion
  • Parameter slider adjusting the velocity
  • x–t graph and quantity readout

Procedure

  1. Read the slope of the x–t graph

    Run the simulation and drag the time slider: the point moves uniformly and the x–t graph is a straight line. Measure the slope Δx/Δt\Delta x/\Delta t between two points and compare with the velocity readout.

  2. Change the velocity

    Drag the parameter slider: higher speed makes the graph steeper and the point travel farther in the same time. Try a negative value: the slope changes sign and the point moves backward — distinguishing signed velocity vv from speed ∣v∣|v|.

  3. Predict a future position

    Pick an instant t not yet reached, compute x=x0+vtx = x_0 + vt from the x0x_0 and vv readouts, then drag the slider to exactly that instant to check the prediction on the figure.

Simulation

Experiment history

Uniform motion at constant velocity contradicted Aristotelian physics, which held that all motion needs a sustaining force. Through inclined-plane experiments (c. 1600–1604) Galileo Galilei argued that a body on a perfectly smooth horizontal plane would move forever: the idea of inertia. René Descartes stated the inertia rule explicitly in 1637–1644; Isaac Newton formalized it as the first law in the Principia (1687): a body free of forces stays at rest or in uniform rectilinear motion. This underlies all classical kinematics.

Related physicists

Galileo GalileiIsaac Newton

Related library topics

Uniform linear motion