A drag racer reaches 150 km/hr in a 2-km race.Assuming constant acceleration,what was the elapsed time for the km (in minutes)?
A)1.4 min
B)1.6 min
C)1.8 min
D)2.0 min
E)2.2 min

Question

Quizplus · Accepted Answer

We can use the formula: 
v = u + at 
where v is the final velocity (150 km/hr), u is the initial velocity (0 km/hr), a is the acceleration, and t is the time taken to cover the distance of 1 km.

Since the car covers 2 km, we need to find the time taken to cover 1 km and double it to get the total time taken.

2 km = (1/2)at^2 
a = (2 km)/(t^2)

Substituting this value of a in the first equation:

150 km/hr = (0 km/hr) + ((2 km)/(t^2))t 
150 km/hr = (2/t) km/hr 
t = (2/150) hr = (2/150) x 60 min = 1.6 min

Therefore, the correct answer is B.

A Drag Racer Reaches 150 Km/hr in a 2-Km Race