A joule is one Newton of force applied over a meter.
For every meter, the brakes put 240000N of force (N=Newtons).
For 40m, multiply the Newtons by 40.
240000N*40=9600000N
Force is defined as the rate of change of momentum.
The initial amount of momentum is

because water stops when it hit the wall total change of momentum must be

.
Now let's calculate the force.

We need to find

. This is the amount of water hiting the wall per second.

Our final formula would be:

And now we can calculate the answer:
Answer:
B train!
Explanation:
A train travelled at 40 km/hr. (120/3)
B train traveled at 45 km/hr (180/4)
Answer:
Tangential acceleration is in the direction of velocity - along the circumference of a circle if the object is undergoing circular motion
a = (V2 - V1) / T
Radial acceleration is perpendicular to the direction of motion if the object is not moving in a straight line (perhaps along the circumference of a circle)
a = m V^2 / R = m ω^2 R where R is the radius vector of the velocity - note that the Radius vector is directed from the center of motion to the object and for circular motion would be constant in magnitude but not in direction