Advertisements
Advertisements
Question
The average time taken by a normal person to react to an emergency is one fifteenth of a second and is called the 'reaction time'. If a bus is moving with a velocity of 60 km/h and its driver sees a child running across the road, how much distance would the bus had moved before he could press the brakes? The reaction time of the people increases when they are intoxicated. How much distance had the bus moved if the reaction time of the driver were 1/2 s under the influence of alcohol?
Advertisements
Solution
Bus is moving with initial velocity of u = 60 km/hr.
60 km/hr = ( 60 X 1000)/3600 = u = 16.66 ms-1.
Reaction time = t =1/15 sec.
Distance would the bus had moved before pressing the bus would be = u X t.
S = 16.66 X 1/15 = 1.1 m.
Now if the driver is intoxiacated then reaction time would be t = 1/2 seconds.
So S becomes S = u X t = 16.66 X 1/2 = 8.33m.
APPEARS IN
RELATED QUESTIONS
The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.
Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school.
If a body traverses a distance in direct proportion to the time, the speed of the body is ______.
Do speed and average speed of a body have the same meaning?
Which is greater?
(i) 60 km/hr
(ii) 15 m/s
A body goes from P to Q with a uniform speed of u and immediately returns back to P at a uniform speed of v. What is the average speed for the whole journey?
Asher says all objects having uniform speed need not have uniform velocity. Give reason.
A car increases its speed from 20 km/h to 50km/h in 10 seconds. Its acceleration is ______.
A bus travels 54 km in 90 minutes. The speed of the bus is ______.
Paheli and Boojho have to cover different distances to reach their school but they take the same time to reach the school. What can you say about their speed?
