It’s going to be both answer A and B but if you can only answer one then it’s going to be B
Answer:
A) The crossbeam is moving relative to the observer on the platform so the height appears contracted.
Explanation:
The observer on the train and the beam are in the same reference frame. That means observer on the train will measure the proper length of the beam not the contracted length . the observer is outside and the plank is in the moving system,it will appear to be moving.
Answer:
p = FΔt = 8.0 N(60 s) = 480 N•s
Explanation:
not asked for, but in that time a frictionless 18 kg mass on a horizontal surface will have change velocity by 480/18 = 26.7 m/s.
An impulse results in a change of momentum.
