force

[no idea]

1.Which newton's law describes inertia is proportional to mass? 1st or 2nd?
2.An object is on a slope, the graph of v-t shows that there is negative acceleration, how do you explain it ?

[vsage]

1. Newton originally dealt with the change of momentum of an object when he conceived the his second law.
2. The only thing I can conclusively say is that the velocity is becoming increasingly negative (which isn't much)

[Astronuc]

http://scienceworld.wolfram.com/physics/topics/GeneralMechanics.html

If the graph v-t shows a negative acceleration, then the object is slowing down.

If the object is traveling up the slope, then kinetic energy is becoming potential energy and perhaps losing some kinetic energy to friction. This presumes also that there is no constant propulsive force on the object.

If the slope is downward, then perhaps the object is slowing due to friction.

And there is always resistance to air or any atmosphere surrounding the object.

Basically, if something is slowing down then the opposing forces exceed the driving (propulsive) forces.