Answer:
875 N
Explanation:
From this question, you didn't state the time taken for the bumper car to move or to hit the other bumper car. In calculations of force, time is often needed, because
Force = mass * acceleration, while
Acceleration = velocity / time, basically
Force = mass * velocity / time.
We have our mass, we have our velocity, but we haven't time. So, for this calculation, I'd assume our time to be 1s.
Going by the formula I stated, we can then say that
Force = 250 * 3.5 / 1
Force = 875 N
This means the force my bumper car have while moving at 3.5 m/s for an estimated time of 1s is 875 N