Absent all other forces, a block sliding down an inclined plane experiences an acceleration =gsin(theta), ie fraction of g. -->Is it safe to say that the block is solely moving under the influence of gravitational force, if so what about the frictional force? Is the force due to gravity > frictional force? -->If we assume the inclined plane to be infinitely long, at what point ( will it only stop at the bottom of the incline and due to what condition does the block come to a stop? Ignoring air resistance -->Work done moving it up directly at height "h" is equal to the work done pulling the block up the distance "d." If there is indeed friction, will the work done pulling the block up d < work done pulling the block at height h? What frictional force is present when we pull the block directly up? --> Lastly, ignoring friction,if the work done is same, then KE is equal and the velocity or rather change in velocity will be sam. If I look according to v=(2gh)^1/2; v'=(2g(h/sintheta)^1/2; v'=velocity moving down the incline is less, which makes sense since the acceleration is less, but doesnt this seem contradicting?