- #1
rohanprabhu
- 414
- 2
Newton's [itex]2^{nd}[/itex] law states that:
Let us assume that a train of 1000 tonnes is moving with a constant velocity [so, [itex]\frac{dp}{dt} = 0[/itex] (p = momentum)] on a rough surface in the [itex]\hat{i}[/itex] direction.
Now, i apply a small force, of a very small magnitude, in the [itex]- \hat{i}[/itex] direction i.e. in the opposite direction of the motion. Will it cause the train's direction to reverse? Here, the force applied by the engine is just enough to counteract the force due to friction. So, even a small force [which i can myself] apply on the train, can i reverse the direction of the train?
I'm asking this because it seems quite like a paradox to me. The 1000 tonnes figure is more or less for the perceptual impact :D.
The rate of change of momentum of a body is proportional to the resultant force acting on the body and is in the same direction.
Let us assume that a train of 1000 tonnes is moving with a constant velocity [so, [itex]\frac{dp}{dt} = 0[/itex] (p = momentum)] on a rough surface in the [itex]\hat{i}[/itex] direction.
Now, i apply a small force, of a very small magnitude, in the [itex]- \hat{i}[/itex] direction i.e. in the opposite direction of the motion. Will it cause the train's direction to reverse? Here, the force applied by the engine is just enough to counteract the force due to friction. So, even a small force [which i can myself] apply on the train, can i reverse the direction of the train?
I'm asking this because it seems quite like a paradox to me. The 1000 tonnes figure is more or less for the perceptual impact :D.