# Motion problem: motorist's braking time including reaction time

• chemie726283
In summary: Add the distances for the two parts.In the summary, In summary, we discussed the calculation of the thinking distance and minimum braking distance for a car traveling at 10m/s with a maximum deceleration rate of 5.0 m/s^2. We also calculated the total minimum stopping distance and examined whether a car traveling at 12 m/s could stop before reaching a stop line 20m away.
chemie726283

## Homework Statement

A motorist is traveling at 10m/s in a car whose maximum deceleration rate is 5.0 m/s^2

The effective reaction time between seeing a hazard and starting to brake is 0.5s

1. Calculate the thinking distance for the drover ar this speed (ie the distance traveled during his reaction time)
2. Calculate the minimim braking distance (ie the distance traveled during maximum deceleration)
3. the total minimum stopping distance at 10 m/s
4. The car approaches traffic lights at 12 m/s and the lights turn red when it is 20m from the line. Show whether it is possible for the car to stop before reaching the line and calculate how far from the line it will stop.

## The Attempt at a Solution

1. s= 10 x 0.5 = 5m
2. s= 10 x 2 x 1/2 x (-5) -> s= 10 m
I am stuck on 3. and 4. and don't know where to start

Last edited by a moderator:
chemie726283 said:
s= 10 x 2 x 1/2 x (-5) -> s= 10 m
10m is right, but I don't understand how you get 10 x 2 x 1/2 x (-5), or how that becomes 10. Looks like -50 to me.
chemie726283 said:
I am stuck on 3.
In part 1 you found the distance traveled before starting to decelerate, and in part 2 the distance while decelerating. Part 3 asks for the total.

## 1. What is the definition of braking time?

Braking time refers to the amount of time it takes for a vehicle to come to a complete stop after the brakes have been applied.

## 2. What factors affect a motorist's braking time?

A motorist's braking time can be affected by several factors, including the speed of the vehicle, the condition of the brakes, the weight of the vehicle, and the road conditions.

## 3. What is reaction time and how does it impact braking time?

Reaction time is the amount of time it takes for a driver to perceive a potential danger and react to it by applying the brakes. This can greatly impact braking time, as a slower reaction time means it will take longer for the driver to start braking and bring the vehicle to a stop.

## 4. How can a motorist's braking time be calculated?

A motorist's braking time can be calculated by adding the reaction time and the actual braking time. The reaction time can be estimated based on factors such as the driver's age and level of alertness. The actual braking time can be measured by conducting tests or using known values for the vehicle's speed and braking distance.

## 5. How can a motorist's braking time be reduced?

A motorist's braking time can be reduced by maintaining a safe speed and distance from other vehicles, regularly maintaining and replacing brakes, and remaining alert and attentive while driving to decrease reaction time.

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