1. Forces and braking
Q1. a. road surface affects the braking distance
b. Tiredness affects the thinking distance
c Poorly maintained brakes affects the braking distance

2. Forces and braking
Q1. a. road surface affects the braking distance
b. Tiredness affects the thinking distance
c Poorly maintained brakes affects the braking distance
Q2. a. At 30mph thinking distance = 30 feet
At 50 mph thinking distance = 50 feet
That is an increase of 20 feet (or 67% increase)
b. At 30mph braking distance = 45 feet
At 50 mph braking distance = 125 feet
That is an increase of 80 feet (or 178% increase)
c. At 30mph stopping distance = 75 feet
At 50 mph stopping distance = 175 feet
That is an increase of 100 feet (or 133% increase)

3. Q3. a. When the speed of a car is doubled
i) the thinking distance is also doubled because
thinking distance = speed x reaction time
ii) the braking distance is more than doubled because
braking distance (s) is proportional to the speed (u) squared

4. Q3. a. When the speed of a car is doubled
i) the thinking distance is also doubled because
thinking distance = speed x reaction time
ii) the braking distance is more than doubled because
braking distance (s) is proportional to the speed (u) squared
b. To check the above relationship with data:
if s ∝ u2 then s = k u2 and s/ u2 = k
data set for 30 mph: 45/ (30) =
data set for 50 mph: / (50) =
Relationship is confirmed as k= for both sets of data

5. Q m= 1500kg u= 31m/s s= 75 m v=0m/s
a) Deceleration a ?
v2 = u2 + 2as
0 = a75
-961 = 150a
-961/ = a = 6.4 m/s2

6. Q m= 1500kg u= 31m/s s= 75 m v=0m/s
a) Deceleration a ?
v2 = u2 + 2as
0 = a75
-961 = 150a
-961/ = a = 6.4 m/s2
m= 1500kg u= 31m/s s= 75 m v=0m/s a = m/s2
b) braking force: F = ma
F = 1500 x -6.4
F = N or kN