Physics 2 — Momentum & Waves

Circular motion

continues from lesson 2 — values defined earlier in the course stay live here

ELI5: moving in a circle at steady speed is still accelerating — your direction keeps changing, and changing velocity needs a force. That force always points to the centre: F = m·v²/r. Take it away (let go of the string) and you fly off straight along the tangent, not outward.

m_{car} := 1500 kg

= 1500 kg

v_{turn} := 19 m/s

= 19 m / s

r_{turn} := 50 m

= 50 m

F_{c} = \frac{m_{car} \cdot v_{turn}^{2}}{r_{turn}}

= 10830 N friction must supply this

✓ pass

F_{c} < 0.8 * m_{car} * 9.81 m/s^2

can dry-road friction (μ ≈ 0.8) hold the turn? (barely)

Real-world hook: centripetal force is why highway curves are banked, why a washing machine spins water out (the drum can't supply the inward force, so water flies off), and what a roller-coaster loop must supply at the top.

Try it yourself: the centripetal force needed for a 1500 kg car at 20 m/s around a 50 m radius. (F = m·v²/r.)

Fc_{you} := 1500 kg * (20 m/s)^2 / 50 m

= 12000 N ✏️ Your turn: compute m·v²/r with m = 1500 kg, v = 20 m/s, r = 50 m. Answer in newtons.

✓ pass

abs(Fc_{you} - 1500 kg * (20 m/s)^2 / 50 m) < 1 N

green when your centripetal force is correct