Question

A sprinter accelerates from rest to a top speed of 24 km/h in 2 seconds and then runs at a constant velocity for the rest of the 100 meter dash,

a- what was the distance he covered in the first 2 seconds

b- what was his time for the whole race

Answer 1

a. 6.67 meters

b. 16 seconds

Step-by-step explanation:

a. v=(24×1000)/3600=6.67 m/s

v=u-at

a=(v-u)/t=(6.67-0)/2=3.335 m/s^2

s=ut+(1/2) at^2 = 0×2+.5×3.335×(2)²=6.67 meters

b. After 2seconds, he ran at a constant velocity. From a, in 2 seconds, he crossed 6.67 meters.

So, distance left =(100-6.67)=93.33 meters

to cross 93.33 meters,he needed,

s=vt

93.33=6.67t

t=13.99≡14 seconds

So, Total (93.33+6.67)=100 meters were covered in (14+2)=16 seconds

Hope, this helps you.