V=(40km/hr)(hr/3600s)(1000000mm/km)
v=11111.1mm/s
v=d/t
d=vt
d=(11111.1mm/s)(5s)
d=55555mm
d=5.56x10^4mm
Kinematics is the study of the motion of a system of bodies without directly considering the forces or potential fields affecting the motion. In other words, kinematics examines how momentum and energy are shared among interacting bodies.
Mass is indirectly proportional to acceleration, so, lighter the object greater would be it's acceleration...
A) 0.10 kg is lightest among them, so it's your answer
The deceleration experienced by the gymnast is the 9 times of the acceleration due to gravity.
Now from Newton`s first law, the net force on gymnast,

Here, W is the weight of the gymnast and a is the acceleration experienced by the gymnast (
acceleration due to gravity)
Therefore,
OR 
Given
and
Substituting these values in above formula and calculate the force exerted by the gymnast,


This number has 3 sig figs.