Speed of the TRAX is given as 16 m/s so let say it is given as

now our speed towards the front end is given by 5 m/s so this is the relative speed of us with respect to TRAX
let say this speed is given as

now we need to find the speed with respect to someone standing outside the TRAX
so here we need to find the net speed in ground frame and hence we can use the formula of relative speed




so someone outside the TRAX will see our speed as 21 m/s
Answer:
position 2
Explanation:
At position 2, the sprinter started running immediately he heard the sound of the gunshot. This shows that the sprinter accelerated from rest and moved with an increasing acceleration. The magnitude of the final force is higher than the magnitude of the initial force at position 2. Therefore, the difference between the final and initial forces (i.e. net force) is forward (or positive).