I have a question that has been puzzling me for a while. When I drive my truck and accelerate hard until 25 mph then put the clutch in to roll freely, the truck will climb a few more mph before beginning to slow down. This is on flat ground or even a slight uphill. The way I see it is as follows. Say acceleration of the truck is 5 ft/s2 (random number). Once the clutch is in the force from the engine is now 0, and therefore acceleration should be 0 unless there is another force pushing the truck forward. However in order to be continuous, acceleration cannot jump from 5 to 0, and will have to decrease continuously. While it is decreasing it is still positive and will cause velocity to climb slowly. Can anyone explain the physics behind this?