1. Reaction Time and Breaking Distance

2. 1. Reaction distance: Distance the vehicle moves during the time it takes to react (reaction time) and apply the brake. Stopping distance: consists of the reaction distance plus the braking distance. v = Δd Δd t t x v = Δd Δd r = v t r

3. 2. Braking distance Depends on two factors: Friction constant (k) A number given to show how slippery it is on a surface. The higher the number, the more slippery. Slippery roads provide less friction with the tires – longer breaking distance. ∆d b = v2v2 k condition of the road. how fast the car is going (and how big it is)

4. Stop distance = Δd r + ∆d b Surface ConditionFriction Constant k (m/s) k (km/hr) Dry0.060.22 Wet0.100.36 Snow / ice0.150.54 Δd r = vt r ∆d b = kv 2

5. Suppose you are riding in a car travelling at 70 km/h or 19.4 m/s on in the rain. You spot a deer in the road. Your reaction time is 1.15 s. What is your stopping distance? v = 19.4 m/s t r = 1.15 sk = 0.10 Stop distance = Δd r + ∆d b Δd r = vt r ∆d b = kv 2 19.41.15 = = 22.3 m = = 37.6 m = 59.9 m 0.1019.4

6. Stop distance = Δd r + ∆d b Surface ConditionFriction Constant k (m/s)k (km/hr) Dry0.060.22 Wet0.100.36 Snow / ice0.150.54 Δd r = vt r ∆d b = kv 2

7. ? Stop distance = Δd r + ∆d b Δd r = vt r ∆d b = kv 2 50 m 70 km/h