Answer:
Well it's mostly about gravity.And when you walk up on a hill that ascends high,you will feel that you are getting pushed back.And a slope makes it more harder if you're pedalling a bike,so you need to use a lot of strength to pedal all the way to the top.In the other hand,when you walk downhill,it feels like your going faster,because your going downward on a slope.And when you ride your bicycle downhill you will accelerate more because you have better air resistance,which make you aerodynamic,and the gravity isn't pushing you that much.So to summarize it's way better if you walk or ride downhill,but be careful cause too much momentum may cause to an accident.
