#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.
Yes......................
Answer:
a) 4.45 m/s
b) 0.9 seconds
Explanation:
t = Time taken
u = Initial velocity
v = Final velocity
s = Displacement
a = Acceleration due to gravity = 9.81 m/s²

a) The vertical speed when the player leaves the ground is 4.45 m/s

Time taken to reach the maximum height is 0.45 seconds

Time taken to reach the ground from the maximum height is 0.45 seconds
b) Time the player stayed in the air is 0.45+0.45 = 0.9 seconds