Saved Bookmarks
| 1. |
a driver driving a truck at a constant speed of 20m/s suddenly saw a parked car ahead of him by 95m. He could apply brake after sometime to produce retardation of 2.5m/s.An accident was avoided. his reaction time is |
|
Answer» Answer: The REACTION time= 11.832 seconds Explanation: Let us FIRST CALCULATE the time needed for the truck to come to rest , that is final velocity v=0 intial velocity u=20m/s, retardation=2.5m/s² time taken t v=u- a×t t= 20÷2.5 t=8s s= u×t- (a×t²)÷2 95= 20t- 1.25t² 1.25t² -20t -95=0 t=19.8s, is the maximum time AVAILABLE to avoid the accident and the time needed to bring the vehicle to rest is 8s therefore the reaction time of the driver = 19.8 - 8 =11.832 s |
|