Answer:
Acceleration: 
Explanation:
The acceleration of an object is equal to the rate of change of velocity:

where
u is the initial velocity
v is the final velocity
t is the time taken for the velocity to change from u to v
For the space probe in this problem, we have:
u = 100 ft/s (initial velocity)
v = 5000 ft/s (final velocity)
t = 0.5 s (time taken)
Therefore, the acceleration is

according to newton's third law, every action has equal and opposite reaction. in this scenario of making a jump from the boat onto a dock, as i jump my feet in contact with the boat push the boat in backward direction. hence the action force is the push by my feet on the boat. the boat reacts by applying a reaction force on my feet pushing the feet in forward direction. hence reaction force here is the force by the boat on the feet. due to the reaction force of the boat on feet, i am pushed in forward direction to reach the the dock.