Who can write the formula of measuring echo distance

Who can write the formula of measuring echo distance

Distance = (time × speed of sound) / 2

What is the echo ranging formula? Junior high school physics

S=Vt/2
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Calculation formula of automobile braking distance
Speed 72km / h, reaction time to stop for 2S, find the braking distance? Write the formula and calculate!
A car is moving at a speed of 72 km / h. when it suddenly sees something in front of it, the driver brakes immediately. Two seconds later, the car stops. How many meters does the car travel from braking to stopping?
"Although you're not very accurate, I'll give you points"

(GB general standard)
S (braking distance) = 0.10v + (the square of V divided by 130),
The reaction distance is v × 1000 × 2.5/3600
Where V is the vehicle speed,
Reaction distance = 72 * 1000 * 2.5 / 3600 = 50m
Braking distance = 0.10 * 50 + (50 * 50 / 130) = 24.23m

Junior high school physics questions speed, reaction distance, braking distance, how to find reaction time
For example, when the speed is 20 km / h, the reaction distance is 4 meters, the braking distance is 2 meters, and the parking distance is 6 meters, how to calculate the reaction time,

Speed v = 20 * 1000 / 3600 = 50 / 9 m / S
Reaction time t '= reaction distance x' / velocity v = 4 / (50 / 9) = 0.72s