Experiment 2 — Stop Before the Cow

Topic: Physics · Class 9 · Equations of motion applied to braking

Aim: Bring the car to a stop within the 40 m before the cow on the road.

Daily: This is the arithmetic behind every speed limit sign, and why “I was only going a bit faster” is such a dangerous sentence. Doubling your speed quadruples your braking distance.

Question: A car doubles its speed. Its braking distance becomes about…

Exp: Braking distance depends on v², from v² = u² + 2as.

Question: Thinking distance depends on…

Exp: The car travels at full speed while you react.

Question: Braking distance from 20 m/s with a = 5 m/s² is…

Exp: s = u² ÷ 2a = 400 ÷ 10 = 40 m.

Question: A wet road mainly reduces…

Exp: Less grip means gentler deceleration and a longer stop.

Question: Which equation gives braking distance directly?

Exp: Rearranged with v = 0, s = u² ÷ 2a.