The net force on a wagon grows while its mass stays the same. What happens to the wagon's acceleration?
A cart sits on a track, held between position marks by a spring. Beata drags the cart to the right, stretching the spring, and lets go. The cart rushes back, overshoots the middle, and ends up oscillating.
The last lesson named the motion. This lesson explains the return: why does an oscillating object keep coming back to its rest position?
Earlier in the course, you saw that a stretched spring exerts a force on whatever it is attached to.
With the cart dragged to the right of its rest position, the stretched spring's force on the cart points left, back toward the rest position.
With the cart on the left of its rest position, the spring is squashed, and its force on the cart points right, back toward the rest position again.
At the rest position itself, the spring is at its natural length, and it exerts no force on the cart.
You have already seen that a net force causes an acceleration. The restoring force therefore accelerates the cart back toward its rest position whenever the cart sits away from it.
The cart arrives at the rest position moving, so it passes through. On the far side, the restoring force points back the other way.
That is the whole story of the oscillation: displaced either way, the cart feels a restoring force toward the rest position, returns, overshoots, and repeats.
Dilys presses the middle of a trampoline bed down with one foot and steps off. The bed springs back up and oscillates about its flat rest position. While the bed is below its rest position, which direction does the restoring force on the bed point?
The bed sits below its flat rest position.
A restoring force always points back toward the rest position.
The restoring force on the bed points upward, toward the flat rest position.
A ruler is clamped flat to a desk with its tip over the edge. Cosmo bends the tip down and releases it. Why does the tip end up oscillating instead of just returning to straight and stopping?
Bent down, the ruler's restoring force points up, toward the straight rest shape, so the tip accelerates upward.
The tip reaches the straight rest shape moving, so it passes through and bends upward.
Bent up, the restoring force points down, back toward the straight rest shape.
At every bent position, the restoring force points back toward the straight rest shape, and the moving tip keeps overshooting it. So the tip oscillates.
A cart on a spring oscillates along a track. At one moment the cart sits to the right of its rest position. Which direction does the restoring force on the cart point?
A mounted door stopper spring oscillates side to side after a flick. At which position is the restoring force on it zero?
Anselm watches a cart oscillating on its spring. He says: 'At every moment the cart sits away from its rest position, the restoring force on it points back toward that rest position.' Is Anselm correct?
Why does an oscillating cart on a spring keep returning to its rest position?
An oscillating cart reaches its rest position moving quickly. What happens next?
Which of these forces is a restoring force?