A person is driving on a level road and see's a sign 180m ahead in the middle of the road. The person strikes the sign at a speed of 60km/h. If the person was travelling at 90km/h when the sign was first spotted what was the students perception-reaction time?
How far back should the student have first observed the sign to be able to stop safely at a comfortable deceleration rate before hitting the sign?
First please tell me what you have as an answer, or what you think it is. Then I will gladly help you!
Hey i got 4.9 seconds as my perception-reaction time. Don't know if this is right though. Not sure how to solve the second part of the question.
To calculate the student's perception-reaction time, we need to find out how much time it took for the student to react after seeing the sign at a different speed.
First, let's convert the speeds from km/h to m/s to have a consistent unit.
Speed at which the person strikes the sign = 60 km/h = (60 * 1000) / 3600 m/s = 16.67 m/s
Speed at which the person spots the sign = 90 km/h = (90 * 1000) / 3600 m/s = 25 m/s
To find the perception-reaction time, we need to determine the difference in time it took the person to react at the two different speeds.
Let's assume that the person reacted just as they spotted the sign.
Perception-reaction time (t) = Time taken to spot the sign at 90 km/h - Time taken to spot the sign at 60 km/h
Now, we need to calculate the distances covered during the perception-reaction time for both speeds.
Distance covered during perception-reaction time at 90 km/h = Speed at which the person spotted the sign * Perception-reaction time
Distance covered during perception-reaction time at 60 km/h = Speed at which the person spotted the sign * Perception-reaction time
Since the person strikes the sign at a distance of 180m, the sum of these distances should be equal to 180m.
Therefore, (Distance covered during perception-reaction time at 90 km/h) + (Distance covered during perception-reaction time at 60 km/h) = 180m
We can rearrange the equation to solve for the perception-reaction time (t):
Distance covered during perception-reaction time at 90 km/h + Distance covered during perception-reaction time at 60 km/h = 180m
(25 m/s * t) + (16.67 m/s * t) = 180m
Now, we can solve this equation to find the perception-reaction time (t).
Once we have the perception-reaction time (t), we can calculate the distance the person should have first observed the sign to be able to stop safely at a comfortable deceleration rate before hitting the sign.
To do this, we need the deceleration rate. If you provide the deceleration rate or any other necessary information, I can help you calculate the required distance.