That depends on the deceleration applied, in which case
time = 2x45 mph/a = 90/a
with a (the deceleration) measured in miles per hour per hour to give the time in hours.
If you mean the time that would be taken using the stopping distances in the UK Highway Code, then, assuming a constant deceleration (from the moment the brakes are applied after the thinking distance):
The stopping distance at 45 mph is 45 ft (thinking distance) + 101.25 ft (braking distance)
[braking distance is speed2 / 20 ft = 452 / 20 ft = 101.25 ft]
The thinking distance is travelled at 45 mph, giving:
think_time = 45 ft / 45 mph
= 45 ft /(45 x 5280 ft / 3600 seconds)
= 45 x 3600 / (45 x 5280) seconds
= 3600/5280 seconds
= 15/22 seconds
(This time is constant for all the emergency stopping distances given in the Highway Code.) Two equations of motion can be used to find the stopping time knowing the initial speed and distance (the final speed is zero):
final_velocity2 = initial_velocity2 + 2 x acceleration x distance
final_velocity = 0
→ acceleration = - initial_velocity2 / (2 x distance)
distance = initial_velocity x time + 1/2 x acceleration x time2
→ distance = initial_velocity x time - (1/4 x initial_velocity2 / distance) x time2
→ time2 - (4 x distance / initial_velocity) x time + 4 x distance2 / initial_velocity2 = 0
→ (time - 2 x distance/initial_velocity)2 = 0
→ breaking_time = 2 x distance / initial_velocity
= 2 x (101.25 ft) / (45 x 5280 / 3600 ft per sec)
= 202.5 x 3600 / (45 x 5280) seconds
= 9x15/2x22
→ total_stopping_time = 15/22 + 9x15/2x22 seconds
= 11x15/2x22 seconds
= 15/4 seconds
= 33/4 seconds
= 3.75 seconds.
To travel 500 feet at 40 mph, it would take about 6 seconds. This is calculated by converting 40 mph to feet per second (40 mph = 58.67 fps) and dividing 500 feet by the speed in feet per second.
At 1000 mph, there are approximately 1467 feet per second.
It takes 51.43 seconds to travel 2,640 feet at 35 mph.
It would take approximately 8 seconds to travel 492.8 feet at a speed of 30 mph.
739.2 feet in six minutes at 1.4 mph
When traveling at 35 mph it will take you 210 feet to come to a complete stop.
When traveling at 35 mph it will take you 210 feet to come to a complete stop
75ft.
about 120 ft
228 ft
62 feet
On dry roads with ABS, around 46 feet.
228 feet
30 feet
Stopping Distance = about 206.25 feet at 55 mph
200 feet
60 feet