Final answer:
3) The trailer is level with the fifth wheel, The trailer should be slightly higher than the fifth wheel to connect properly to the tractor. An empty trailer is more likely to exhibit slow bouncing on the highway because it lacks the stabilizing effect of a heavy load.
Step-by-step explanation:
The trailer is at the right height when it is slightly higher than the fifth wheel. This allows the trailer to be lowered onto the fifth wheel as the tractor is backed under it, ensuring a secure coupling without causing damage to the equipment. Positioning the trailer higher than the fifth wheel makes the coupling process smoother and typically indicates proper height for hookup, provided it's not excessively high.
Regarding the observation of a trailer bouncing up and down slowly on the highway, a trailer that is nearly empty is more likely to bounce than one that is heavily loaded. A heavy load provides stability to the trailer's suspension system, reducing the bouncing effect. An empty or lightly loaded trailer lacks this weight, and thus, the suspension is less damped, resulting in more pronounced and slower bouncing movements.