physics
posted by michaela .
A 10,000 kg frieight car is rolling along a track at 3.0 m/s. Calculate the time needed for a force of 1000 N to stop the car.

force*time= mass*changeinvelocity
1000t=10,000*3
solve for t,in seconds 
Force = change in momentum/change in time = ma
1000 = (10,000*3)/ change in time
change in time = 10*3 = 30 seconds