Puck on Ice
A puck sliding on a surface with adjustable friction — from frictionless to high friction, watch inertia in action as the puck maintains or loses velocity.
Objective
Verify Newton's First Law — an object in motion remains in motion at constant velocity unless acted on by a net force. With friction coefficient μk set to zero, the puck slides indefinitely; as μk increases, kinetic friction decelerates the puck according to a = μk · g, and the puck stops at distance d = v₀² / (2 · μk · g). The simulation assumes a flat horizontal surface, point-mass puck, and no air resistance.
Setup
- Set Friction (μk) to 0.00 and Initial Speed to 10 m/s. Press Start — observe the puck sliding at constant speed across the full canvas without slowing.
- Note the Speed readout: it should remain at 10.00 m/s throughout the run (frictionless inertia). The simulation stops at t = 30 s via the time cap.
- Press Reset. Now set Friction (μk) to 0.10 and Initial Speed to 10 m/s. Press Start and note when the puck stops — the Distance readout should reach approximately 51 m.
- Press Reset. Set Friction (μk) to 0.50 and Initial Speed to 10 m/s. Press Start — the puck should stop in approximately 10.2 m, roughly five times sooner.
- Note the Speed and Kin. Energy readouts at t = 1 s for each of the three friction values (0.00, 0.10, 0.50) — record them in a notebook between runs to compare how quickly friction removes energy (Reset clears the on-screen history).
Analytical Prediction
With μk = 0.10, v₀ = 10 m/s, and g = 9.8 m/s², the deceleration and stopping distance are:
The puck stops after traveling approximately 51.0 m, which the Distance readout should display at halt. With μk = 0.50 the deceleration is 4.9 m/s² and stopping distance ≈ 10.2 m. With μk = 0.00 the deceleration is exactly zero — the puck never stops and the Speed readout holds at 10.00 m/s until the 30 s time cap.
Results Analysis
After each run, compare the Distance readout at halt to the analytical prediction. For μk = 0.10, the Distance readout should read approximately 51.0 m (±0.5 m). For μk = 0.50 it should read approximately 10.2 m. The Speed readout should reach 0.00 when the puck stops. In the frictionless run (μk = 0), Speed should remain constant at the initial value for the full 30 s, confirming Newton's First Law directly — the net force is zero, so velocity cannot change. The Kin. Energy readout mirrors the square of the speed, dropping to zero when the puck halts.
Source of Error
The model treats the puck as a point mass on a perfectly flat, rigid surface with no air resistance, no rolling resistance, and no rotational inertia. Real ice pucks experience a small viscous drag component and pressure-melting lubrication that reduces μk below the value for dry surfaces — this sim uses a single μk value as a tuneable parameter. The analytical prediction assumes the same point-mass, constant-μk model, so the two share identical idealizations and any residual gap is purely numerical.
Further Exploration
- Set μk = 0 and vary the Initial Speed from 1 to 20 m/s. Does the puck's speed during the run change? Why does Newton's First Law predict it should not, regardless of the initial value?
- Find the Initial Speed that causes the puck to travel exactly 20 m with μk = 0.20. Use the formula d = v₀² / (2 · μk · g) to predict the answer first, then verify with the Distance readout.
- Double the friction coefficient from 0.10 to 0.20 while keeping v₀ = 10 m/s. Does the stopping distance halve? Use the simulation to check whether the relationship d ∝ 1/μk holds.
- Set μk = 0.50 and compare the Distance readout for v₀ = 5 m/s versus v₀ = 10 m/s. The formula predicts the ratio should be 1:4 — does the simulation agree?