#2
As it is given here
initial speed is
After 4 seconds the final speed is
so here we can use the formula of acceleration using kinematics
so here it will accelerate at 2 m/s^2 rate.
#3
As it is given here
initial it starts from rest
After 2.5 seconds the final speed is
so here we can use the formula of acceleration using kinematics
so here it will accelerate at 6 m/s^2 rate.
#4
i think question is not correct as in first line it is saying about a bag of trash and then in next line it is asking for the position of Jumper and bridge.