Physics
Physics
Problem
4.3 Give the magnitude and direction of the net force acting on a stone of mass 0.1 kg , (a) just after it is dropped from the window of a stationary train, (b) just after it is dropped from the window of a train running at a constant velocity of , (c) just after it is dropped from the window of a train accelerating with , (d) lying on the floor of a train which is accelerating with , the stone being at rest relative to the train. Neglect air resistance throughout.Intuitive explanation
The key insight is that the net force on an object depends only on its acceleration in an inertial reference frame—not on the motion of whatever released it. Once the stone leaves the train, gravity is the only real force acting on it; the train's velocity or acceleration becomes irrelevant. For the stone on the accelerating train floor, you must account for the normal force that keeps it accelerating with the train.
Intuitive explanation
The key insight is that the net force on an object depends only on its acceleration in an inertial reference frame—not on the motion of whatever released it. Once the stone leaves the train, gravity is the only real force acting on it; the train's velocity or acceleration becomes irrelevant. For the stone on the accelerating train floor, you must account for the normal force that keeps it accelerating with the train.