Passage I
Students used 2 methods to calculate D, a car’s total stopping distance; D is the distance a car travels from the time a driver first reacts to an emergency until the car comes to a complete stop.
In Method 1, R is the distance a car travels during a driver’s assumed reaction time of 0.75 sec, and B is the average distance traveled once the brakes are applied. Method 2 assumes that D = initial speed in ft/secｘ2 sec. Table 1 lists R, B, and D for various initial speeds, where D was computed using both methods. Figure 1 contains graphs of D versus initial speed for Method 1 and Method 2.
Table 1 and Figure 1 adapted from Edwin F. Meyer III, Multiple-Car Pileups and the Two-Second Rule. ©1994 by The American Association of Physics Teachers.
5. Based on Table 1 or Figure 1, if the initial speed of a car is 90 mi/hr, D, according to Method 2, will be:
Your Answer is
Correct Answer is D
Explanation
It can be seen from table 1 that when the initial speed increases by 20 mi/hr, the D obtained by Method 2 increases by about 60ft.
So it can be estimated that when the initial speed is 90, the D calculated by Method 2 is about 266 ft