I believe the answer is a

where:
F - force
m - mass
a - acceleration
We transform this formula to get a:

Answer:
Bent knees
Explanation:
Depending the height your jumping from, if you were jumping from a high structure it's best if you jump and land on knees so you dont sprang your ankles from jumping and landing on your straight legs, you could even pull a muscle if you land on straight legs.
The formula for getting the distance will be distance = speed x time
D = S x T
speed or velocity = 50km/h
time = 0.5 h
the equation will be done directly because it's already in it's SI units
distance = 50km/h x 0.5h
hour cancels hour and the equation remains = 50km x 0.5
Ans = 25 km
the train will move 25 km far in 0.5h