Question

A person running a 100 m race is at the starting blocks waiting for the race to begin. At the starters call, the runner starts sprinting. The runner reaches a maximum velocity of 8.9 m/s at the finish line. It takes the runner 12 seconds to reach the finish line. After crossing the finish line, it takes the runner 16 seconds before coming to a complete stop 25 meters later. What is the average acceleration of the runner from the start of the race until the finish line?
@irishboy123

Answer 1

you go first , mate!

your answer is ... ?

Answer 2

.74166 m/s

Answer 3

lol!!

Answer 4

let me have a go

Answer 5

ok

Answer 6

@IrishBoy123

Answer 7

\(\bar a = \dfrac{\Delta v}{\Delta t}\)

over the course of the race we can say that:
\(\Delta v = 0\)

\(\implies \bar a = 0\)

Answer 8

where \(\bar a\) is the average acceleration

Answer 9

8.9/12 @IrishBoy123

Answer 10

Nah mate

I'd go with gut instinct

\(\bar a = \dfrac{\Delta v}{\Delta t}\)

\(\Delta v = 0 \implies \bar a = 0\)

Answer 11

0.74 m/s2

1.6 m/s2

0.56 m/s2

8.3 m/s2
these are my options @IrishBoy123

Answer 12

?

Answer 13

@mathmale

Answer 14

you can use an Equation of Motion

\(x = u t + {1 \over 2}a t^2\)

to arrive at

\(a = \dfrac {2x}{t^2}\)

\( = \dfrac {2(125)}{28^2} = 0.319\)

Answer 15

\(\color{#0cbb34}{\text{Originally Posted by}}\) @IrishBoy123
but i still think the proper answer is zero :-))
\(\color{#0cbb34}{\text{End of Quote}}\)