Question

A certain drag racer can accelerate from 0 to 90 km/h in 5.0 s. (a) What is its average acceleration, in g’s, during this time? (b) How far will it travel during the 5.0 s, assuming its acceleration to be constant? (c) How much time would be required to go a distance of 0.5 km if the acceleration could be maintained at the same value?

Answer 1

Hello Dear.

Here is your answer---

Given---

(a)  Initial Velocity(u) = 0 km/hr.
                                 = 0 m/s.

Final Velocity(v) = 90 km/hr.
                          = 90 x 5/18 (changing into m/s)
                          =  25 m/s 

         Time (t) = 5 sec
   
Acceleration =    $\frac{v-u}{t}$ 
    
                    =    $\frac{25-0}{5}$ 
                 
                    =    5m/s²


(b)  
         Speed = 90 Km/hr.
                    = 25 m/s.

         Time =  5 sec.

Using the formula
          Speed = distance /time
  ⇒ Distance = Speed × Time
                     = 25 × 5
                     = 125 m.

(c) Now, Distance = 0.5 km
                            = 0.5 × 1000 m
                            = 500 m.
 
Speed = 25 m/s [ Since the acceleration is constant]

Thus, Time = Distance/Speed
                   = 500/25
                   = 20 seconds.


Hope it helps.

Have a Marvelous Day.