Question

a sprinter accelerates to his maximum speed in 4 seconds . if such a sprinter finisher a 140 m race in 9 seconds what is his acceleration in the first 4 seconds

Answer 1

Answer:

The sprinter reached his maximum acceleration in 4secs , means there is no acceleration for the rest of the 5 secs in the 9 secs;

s = ut + 1/2 at²

Then;first you have to find the velocity for the first 4 secs = 140m/9secs

≈ 15.6 m/s

= 15.6 = 4u + 1/2 [9]² [or] 140/9 = 4u + 1/2 [9]²

= 15.6 = 4u + 0.5

= 4u = 15.6 - 0.5

= 4u = 15.056

u = 15.056/4

u = 3.76

u ≈ 4

Then ;

v² = u² + 2as

v² = [3.76]² + 2 x a x 4

v² = 14.1 + 8a

8a = v² - 14.1

a = v² - 14.1 / 8

a = v - [3.76] /4

a = v - u /t

a =  3.76 + 4a - 4 / 4

In standarad form ; the acceleration for the first  4 secs =

4a - 0.236/4