Asports car accelerates from 0 to 30 mph in 1.5 s. how long would it take to accelerate from 0 to 60 mph, assuming the power of the engine to be independent of velocity and neglecting air drag?

6 s

Explanation:

given,

Sports car accelerate from 0 to 30 mph in 1.5 s

time taken to accelerate  0 to 60 mph = ?

The power of the engine is independent of velocity and neglecting friction

power =

P = constant  

the kinetic energy for 60 mph larger than this of 30 mph

 =

 =

 =

 = 4

gain in kinetic energy  = P x t

time = 4 x 1.5

       = 6 s

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.